WorldWideScience

Sample records for model realistic inlet

  1. Coastal Inlet Model Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Coastal Inlet Model Facility, as part of the Coastal Inlets Research Program (CIRP), is an idealized inlet dedicated to the study of coastal inlets and equipped...

  2. Climate Change Impacts on the Stability of Small Tidal Inlets: A Numerical Modelling Study Using the Realistic Analogue Approach

    Directory of Open Access Journals (Sweden)

    Trang Minh Duong

    2012-09-01

    Full Text Available Tidal inlets are of great societal importance as they are often associated with ports and harbours, industry, tourism, recreation and prime waterfront real estate. Their behaviour is governed by the delicate balance of oceanic processes (tides, waves and mean sea level, and fluvial/estuarine processes (riverflow and heat fluxes, all of which can be significantly affected by climate change (CC processes. This study investigates the potential range of CC impacts on the stability (closed/open state and locational stability via the application of a sophisticated process based morphodynamic model (Delft3D to strategically selected schematized inlet morphologies and forcing conditions. Results show that, under worst case scenario conditions, the integrated effect of climate change driven increase in mean sea level, wave height and wave angle may significantly change inlet stability condition.

  3. Climate change impacts on the stability of small tidal inlets: A numerical modelling study using Realistic Analogue approach

    NARCIS (Netherlands)

    Duong, T.; Ranasinghe, R.; Luijendijk, A.; Dastgheib, A.; Roelvink, D.

    2012-01-01

    Tidal inlets are of great societal importance as they are often associated with ports and harbours, industry, tourism, recreation and prime waterfront real estate. Their behaviour is governed by the delicate balance of oceanic processes (tides, waves and mean sea level), and fluvial/estuarine proces

  4. Is realistic neuronal modeling realistic?

    Science.gov (United States)

    Almog, Mara; Korngreen, Alon

    2016-11-01

    Scientific models are abstractions that aim to explain natural phenomena. A successful model shows how a complex phenomenon arises from relatively simple principles while preserving major physical or biological rules and predicting novel experiments. A model should not be a facsimile of reality; it is an aid for understanding it. Contrary to this basic premise, with the 21st century has come a surge in computational efforts to model biological processes in great detail. Here we discuss the oxymoronic, realistic modeling of single neurons. This rapidly advancing field is driven by the discovery that some neurons don't merely sum their inputs and fire if the sum exceeds some threshold. Thus researchers have asked what are the computational abilities of single neurons and attempted to give answers using realistic models. We briefly review the state of the art of compartmental modeling highlighting recent progress and intrinsic flaws. We then attempt to address two fundamental questions. Practically, can we realistically model single neurons? Philosophically, should we realistically model single neurons? We use layer 5 neocortical pyramidal neurons as a test case to examine these issues. We subject three publically available models of layer 5 pyramidal neurons to three simple computational challenges. Based on their performance and a partial survey of published models, we conclude that current compartmental models are ad hoc, unrealistic models functioning poorly once they are stretched beyond the specific problems for which they were designed. We then attempt to plot possible paths for generating realistic single neuron models. Copyright © 2016 the American Physiological Society.

  5. Unsteady lubrication modeling of inlet zone in metal rolling processes

    Institute of Scientific and Technical Information of China (English)

    毛明智; 谭建平

    2002-01-01

    An unsteady lubrication model of inlet zone in metal rolling was established. The simulation computations show that for the variation amplitude of the inlet film thickness, the variation of the inlet angle contributes the largest, the surface mean speed contributes the second and the back tension stress the least. The higher the input frequency is, the smaller the amplitude output of the inlet film thickness will be. For a sinusoidal input, the inlet film thickness varies periodically but is not a sine wave because the system is not linear.

  6. Long-Term Morphological Modeling of Barrier Island Tidal Inlets

    Directory of Open Access Journals (Sweden)

    Richard Styles

    2016-09-01

    Full Text Available The primary focus of this study is to apply a two-dimensional (2-D coupled flow-wave-sediment modeling system to simulate the development and growth of idealized barrier island tidal inlets. The idealized systems are drawn from nine U.S. coastal inlets representing Pacific Coast, Gulf Coast and Atlantic Coast geographical and climatological environments. A morphological factor is used to effectively model 100 years of inlet evolution and the resulting morphological state is gauged in terms of the driving hydrodynamic processes. Overall, the model performs within the range of established theoretically predicted inlet cross-sectional area. The model compares favorably to theoretical models of maximum inlet currents, which serve as a measure of inlet stability. Major morphological differences are linked to inlet geometry and tidal forcing. Narrower inlets develop channels that are more aligned with the inlet axis while wider inlets develop channels that appear as immature braided channel networks similar to tidal flats in regions with abundant sediment supply. Ebb shoals with strong tidal forcing extend further from shore and spread laterally, promoting multi-lobe development bisected by ebb shoal channels. Ebb shoals with moderate tidal forcing form crescent bars bracketing a single shore-normal channel. Longshore transport contributes to ebb shoal asymmetry and provides bed material to help maintain the sediment balance in the bay.

  7. Development of a realistic human airway model.

    Science.gov (United States)

    Lizal, Frantisek; Elcner, Jakub; Hopke, Philip K; Jedelsky, Jan; Jicha, Miroslav

    2012-03-01

    Numerous models of human lungs with various levels of idealization have been reported in the literature; consequently, results acquired using these models are difficult to compare to in vivo measurements. We have developed a set of model components based on realistic geometries, which permits the analysis of the effects of subsequent model simplification. A realistic digital upper airway geometry except for the lack of an oral cavity has been created which proved suitable both for computational fluid dynamics (CFD) simulations and for the fabrication of physical models. Subsequently, an oral cavity was added to the tracheobronchial geometry. The airway geometry including the oral cavity was adjusted to enable fabrication of a semi-realistic model. Five physical models were created based on these three digital geometries. Two optically transparent models, one with and one without the oral cavity, were constructed for flow velocity measurements, two realistic segmented models, one with and one without the oral cavity, were constructed for particle deposition measurements, and a semi-realistic model with glass cylindrical airways was developed for optical measurements of flow velocity and in situ particle size measurements. One-dimensional phase doppler anemometry measurements were made and compared to the CFD calculations for this model and good agreement was obtained.

  8. Recent tests of realistic models

    Energy Technology Data Exchange (ETDEWEB)

    Brida, Giorgio; Degiovanni, Ivo Pietro; Genovese, Marco; Gramegna, Marco; Piacentini, Fabrizio; Schettini, Valentina; Traina, Paolo, E-mail: m.genovese@inrim.i [Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino (Italy)

    2009-06-01

    In this article we present recent activity of our laboratories on testing specific hidden variable models and in particular we discuss the realizations of Alicki - van Ryn test and tests of SED and of Santos' models.

  9. Particle deposition in a realistic geometry of the human conducting airways: Effects of inlet velocity profile, inhalation flowrate and electrostatic charge.

    Science.gov (United States)

    Koullapis, P G; Kassinos, S C; Bivolarova, M P; Melikov, A K

    2016-07-26

    Understanding the multitude of factors that control pulmonary deposition is important in assessing the therapeutic or toxic effects of inhaled particles. The use of increasingly sophisticated in silico models has improved our overall understanding, but model realism remains elusive. In this work, we use Large Eddy Simulations (LES) to investigate the deposition of inhaled aerosol particles with diameters of dp=0.1,0.5,1,2.5,5 and 10μm (particle density of 1200kg/m(3)). We use a reconstructed geometry of the human airways obtained via computed tomography and assess the effects of inlet flow conditions, particle size, electrostatic charge, and flowrate. While most computer simulations assume a uniform velocity at the mouth inlet, we found that using a more realistic inlet profile based on Laser Doppler Anemometry measurements resulted in enhanced deposition, mostly on the tongue. Nevertheless, flow field differences due to the inlet conditions are largely smoothed out just a short distance downstream of the mouth inlet as a result of the complex geometry. Increasing the inhalation flowrate from sedentary to activity conditions left the mean flowfield structures largely unaffected. Nevertheless, at the higher flowrates turbulent intensities persisted further downstream in the main bronchi. For dp>2.5μm, the overall Deposition Fractions (DF) increased with flowrate due to greater inertial impaction in the oropharynx. Below dp=1.0μm, the DF was largely independent of particle size; it also increased with flowrate, but remained significantly lower. Electrostatic charge increased the overall DF of smaller particles by as much as sevenfold, with most of the increase located in the mouth-throat. Moreover, significant enhancement in deposition was found in the left and right lung sub-regions of our reconstructed geometry. Although there was a relatively small impact of inhalation flowrate on the deposition of charged particles for sizes dp<2.5μm, impaction prevailed over

  10. Modelling Complex Inlet Geometries in CFD

    DEFF Research Database (Denmark)

    Skovgaard, M.; Nielsen, Peter V.

    Modem inlet devices applied in the field of ventilation of rooms are getting more complex in terms of geometry in order to fulfil the occupants' demand for thermal comfort in the room and in order to decrease the energy consumption. This expresses the need for a more precise calculation of the fl...... and tested. The method is based upon threedimensional - and radial wall jet theory and upon diffuser specific experimental data....

  11. Realistic face modeling based on multiple deformations

    Institute of Scientific and Technical Information of China (English)

    GONG Xun; WANG Guo-yin

    2007-01-01

    On the basis of the assumption that the human face belongs to a linear class, a multiple-deformation model is proposed to recover face shape from a few points on a single 2D image. Compared to the conventional methods, this study has the following advantages. First, the proposed modified 3D sparse deforming model is a noniterative approach that can compute global translation efficiently and accurately. Subsequently, the overfitting problem can be alleviated based on the proposed multiple deformation model. Finally, by keeping the main features, the texture generated is realistic. The comparison results show that this novel method outperforms the existing methods by using ground truth data and that realistic 3D faces can be recovered efficiently from a single photograph.

  12. Realistic molecular model of kerogen's nanostructure

    Science.gov (United States)

    Bousige, Colin; Ghimbeu, Camélia Matei; Vix-Guterl, Cathie; Pomerantz, Andrew E.; Suleimenova, Assiya; Vaughan, Gavin; Garbarino, Gaston; Feygenson, Mikhail; Wildgruber, Christoph; Ulm, Franz-Josef; Pellenq, Roland J.-M.; Coasne, Benoit

    2016-05-01

    Despite kerogen's importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen's chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental-simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen's nanostructure without considering the presence of clays and other minerals in shales. We probe the models' strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen's maturation, which manifests itself as an increase in the sp2/sp3 hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms.

  13. Realistic molecular model of kerogen's nanostructure.

    Science.gov (United States)

    Bousige, Colin; Ghimbeu, Camélia Matei; Vix-Guterl, Cathie; Pomerantz, Andrew E; Suleimenova, Assiya; Vaughan, Gavin; Garbarino, Gaston; Feygenson, Mikhail; Wildgruber, Christoph; Ulm, Franz-Josef; Pellenq, Roland J-M; Coasne, Benoit

    2016-05-01

    Despite kerogen's importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen's chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental-simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen's nanostructure without considering the presence of clays and other minerals in shales. We probe the models' strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen's maturation, which manifests itself as an increase in the sp(2)/sp(3) hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms.

  14. Cellular automaton for realistic modelling of landslides

    CERN Document Server

    Segrè, E; Enrico Segre; Chiara Deangeli

    1994-01-01

    We develop a numerical model for the simulation of debris flow in landslides over a complex three dimensional topography. The model is based on a lattice, in which debris can be transferred among nearest neighbours according to established empirical relationships for granular flows. The model is validated comparing its results with reported field data. Our model is in fact a realistic elaboration of simpler ``sandpile automata'', which have in recent years been studied as supposedly paradigmatic of ``self organized criticality''. Statistics and scaling properties of the simulation are examined, showing that the model has an intermittent behaviour.

  15. Realistic model for radiation-matter interaction

    CERN Document Server

    Pakula, R A

    2004-01-01

    This paper presents a realistic model that describes radiation-matter interactions. This is achieved by a generalization of first quantization, where the Maxwell equations are interpreted as the electromagnetic component of the Schrodinger equation. This picture is complemented by the consideration of electrons and photons as real particles in three-dimensional space, following guiding conditions derived from the particle-wave-functions to which they are associated. The guiding condition for the electron is taken from Bohmian mechanics, while the photon velocity is defined as the ratio between the Poynting vector and the electromagnetic energy density. The case of many particles is considered, taking into account their statistical properties. The formalism is applied to a two level system, providing an intuitive description for spontaneous emission, Lamb shift, scattering, absorption, dispersion, resonance fluorescence and vacuum fields. This model describes quantum jumps by the entanglement between the photo...

  16. Sialendoscopy Training: Presentation of a Realistic Model.

    Science.gov (United States)

    Pascoto, Gabriela Robaskewicz; Stamm, Aldo Cassol; Lyra, Marcos

    2017-01-01

    Introduction Several surgical training simulators have been created for residents and young surgeons to gain experience with surgical procedures. Laboratory training is fundamental for acquiring familiarity with the techniques of surgery and skill in handing instruments. Objective The aim of this study is to present a novel simulator for training sialendoscopy. Method This realistic simulator was built with a synthetic thermo-retractile, thermo-sensible rubber which, when combined with different polymers, produces more than 30 different formulas. These formulas present textures, consistencies, and mechanical resistance are similar to many human tissues. Results The authors present a training model to practice sialendoscopy. All aspects of the procedure are simulated: month opening, dilatation of papillae, insert of the scope, visualization of stones, extraction of these stones with grasping or baskets, and finally, stone fragmentation with holmium laser. Conclusion This anatomical model for sialendoscopy training should be considerably useful to abbreviate the learning curve during the qualification of young surgeons while minimizing the consequences of technical errors.

  17. Observations and modeling of a tidal inlet dye tracer plume

    Science.gov (United States)

    Feddersen, Falk; Olabarrieta, Maitane; Guza, R. T.; Winters, D.; Raubenheimer, Britt; Elgar, Steve

    2016-10-01

    A 9 km long tracer plume was created by continuously releasing Rhodamine WT dye for 2.2 h during ebb tide within the southern edge of the main tidal channel at New River Inlet, NC on 7 May 2012, with highly obliquely incident waves and alongshore winds. Over 6 h from release, COAWST (coupled ROMS and SWAN, including wave, wind, and tidal forcing) modeled dye compares well with (aerial hyperspectral and in situ) observed dye concentration. Dye first was transported rapidly seaward along the main channel and partially advected across the ebb-tidal shoal until reaching the offshore edge of the shoal. Dye did not eject offshore in an ebb-tidal jet because the obliquely incident breaking waves retarded the inlet-mouth ebb-tidal flow and forced currents along the ebb shoal. The dye plume largely was confined to <4 m depth. Dye was then transported downcoast in the narrow (few 100 m wide) surfzone of the beach bordering the inlet at 0.3 m s-1 driven by wave breaking. Over 6 h, the dye plume is not significantly affected by buoyancy. Observed dye mass balances close indicating all released dye is accounted for. Modeled and observed dye behaviors are qualitatively similar. The model simulates well the evolution of the dye center of mass, lateral spreading, surface area, and maximum concentration, as well as regional ("inlet" and "ocean") dye mass balances. This indicates that the model represents well the dynamics of the ebb-tidal dye plume. Details of the dye transport pathways across the ebb shoal are modeled poorly perhaps owing to low-resolution and smoothed model bathymetry. Wave forcing effects have a large impact on the dye transport.

  18. Algorithm for Realistic Modeling of Graphitic Systems

    Directory of Open Access Journals (Sweden)

    A.V. Khomenko

    2011-01-01

    Full Text Available An algorithm for molecular dynamics simulations of graphitic systems using realistic semiempirical interaction potentials of carbon atoms taking into account both short-range and long-range contributions is proposed. Results of the use of the algorithm for a graphite sample are presented. The scalability of the algorithm depending on the system size and the number of processor cores involved in the calculations is analyzed.

  19. Modelling Morphological Response of Large Tidal Inlet Systems to Sea Level Rise

    NARCIS (Netherlands)

    Dissanayake, P.K.

    2011-01-01

    This dissertation qualitatively investigates the morphodynamic response of a large inlet system to IPCC projected relative sea level rise (RSLR). Adopted numerical approach (Delft3D) used a highly schematised model domain analogous to the Ameland inlet in the Dutch Wadden Sea. Predicted inlet evolut

  20. Mechanics and rates of tidal inlet migration: Modeling and application to natural examples

    Science.gov (United States)

    Nienhuis, Jaap H.; Ashton, Andrew D.

    2016-11-01

    Tidal inlets on barrier coasts can migrate alongshore hundreds of meters per year, often presenting great management and engineering challenges. Here we perform model experiments with migrating tidal inlets in Delft3D-SWAN to investigate the mechanics and rates of inlet migration. Model experiments with obliquely approaching waves suggest that tidal inlet migration occurs due to three mechanisms: (1) littoral sediment deposition along the updrift inlet bank, (2) wave-driven sediment transport preferentially eroding the downdrift bank of the inlet, and (3) flood-tide-driven flow preferentially cutting along the downdrift inlet bank because it is less obstructed by flood-tidal delta deposits. To quantify tidal inlet migration, we propose and apply a simple mass balance framework of sediment fluxes around inlets that includes alongshore sediment bypassing and flood-tidal delta deposition. In model experiments, both updrift littoral sediment and the eroded downdrift inlet bank are sediment sources to the growing updrift barrier and the flood-tidal delta, such that tidal inlets can be net sink of up to 150% of the littoral sediment flux. Our mass balance framework demonstrates how, with flood-tidal deltas acting as a littoral sediment sink, migrating tidal inlets can drive erosion of the downdrift barrier beach. Parameterizing model experiments, we propose a predictive model of tidal inlet migration rates based upon the relative momentum flux of the inlet jet and the alongshore radiation stress; we then compare these predicted migration rates to 22 natural tidal inlets along the U.S. East Coast and find good agreement.

  1. Particle deposition in a realistic geometry of the human conducting airways: Effects of inlet velocity profile, inhalation flowrate and electrostatic charge

    DEFF Research Database (Denmark)

    Koullapis, P. G.; Kassinos, S. C.; Bivolarova, Mariya Petrova

    2016-01-01

    Understanding the multitude of factors that control pulmonary deposition is important in assessing the therapeutic or toxic effects of inhaled particles. The use of increasingly sophisticated in silico models has improved our overall understanding, but model realism remains elusive. In this work......, we use Large Eddy Simulations (LES) to investigate the deposition of inhaled aerosol particles with diameters of dp=0.1,0.5,1,2.5,5dp=0.1,0.5,1,2.5,5 and 10μm (particle density of 1200 kg/m3). We use a reconstructed geometry of the human airways obtained via computed tomography and assess the effects....... Nevertheless, flow field differences due to the inlet conditions are largely smoothed out just a short distance downstream of the mouth inlet as a result of the complex geometry. Increasing the inhalation flowrate from sedentary to activity conditions left the mean flowfield structures largely unaffected...

  2. Three-neutron resonance trajectories for realistic interaction models

    CERN Document Server

    Lazauskas, R

    2005-01-01

    Three-neutron resonances are searched using realistic nucleon-nucleon interaction models. Resonance pole trajectories were explored by artificially binding three-neutron and then gradually removing additional interaction. The final pole positions for three-neutron states up to $|J|$=5/2 finish in the fourth energy quadrant with Re(E)$\\leqslant0$ before additional interaction is removed. This study shows that realistic nucleon-nucleon interaction models exclude possible existence of observable three-neutron resonances.

  3. Realistic coasting cosmology from the Milne model

    CERN Document Server

    John, Moncy V

    2016-01-01

    In the context of the recent synchronicity problem in $\\Lambda$CDM cosmology, coasting models such as the classic Milne model and the $R_h=ct$ model have attracted much attention. Also, a very recent analysis of supernovae Ia data is reported to favour models with constant expansion rates. We point out that the nonempty $R_h=ct$ model has some known antecedents in the literature. Some of these are published even before the discovery of the accelerated expansion and were shown to have none of the cosmological problems and also that $H_0t_0=1$ and $\\Omega_m/\\Omega_{dark \\; energy}$ = some constant of the order of unity. In this paper, we also derive such a model by a complex extension of scale factor in the Milne model.

  4. A Computational Framework for Realistic Retina Modeling.

    Science.gov (United States)

    Martínez-Cañada, Pablo; Morillas, Christian; Pino, Begoña; Ros, Eduardo; Pelayo, Francisco

    2016-11-01

    Computational simulations of the retina have led to valuable insights about the biophysics of its neuronal activity and processing principles. A great number of retina models have been proposed to reproduce the behavioral diversity of the different visual processing pathways. While many of these models share common computational stages, previous efforts have been more focused on fitting specific retina functions rather than generalizing them beyond a particular model. Here, we define a set of computational retinal microcircuits that can be used as basic building blocks for the modeling of different retina mechanisms. To validate the hypothesis that similar processing structures may be repeatedly found in different retina functions, we implemented a series of retina models simply by combining these computational retinal microcircuits. Accuracy of the retina models for capturing neural behavior was assessed by fitting published electrophysiological recordings that characterize some of the best-known phenomena observed in the retina: adaptation to the mean light intensity and temporal contrast, and differential motion sensitivity. The retinal microcircuits are part of a new software platform for efficient computational retina modeling from single-cell to large-scale levels. It includes an interface with spiking neural networks that allows simulation of the spiking response of ganglion cells and integration with models of higher visual areas.

  5. Biophysically realistic minimal model of dopamine neuron

    Science.gov (United States)

    Oprisan, Sorinel

    2008-03-01

    We proposed and studied a new biophysically relevant computational model of dopaminergic neurons. Midbrain dopamine neurons are involved in motivation and the control of movement, and have been implicated in various pathologies such as Parkinson's disease, schizophrenia, and drug abuse. The model we developed is a single-compartment Hodgkin-Huxley (HH)-type parallel conductance membrane model. The model captures the essential mechanisms underlying the slow oscillatory potentials and plateau potential oscillations. The main currents involved are: 1) a voltage-dependent fast calcium current, 2) a small conductance potassium current that is modulated by the cytosolic concentration of calcium, and 3) a slow voltage-activated potassium current. We developed multidimensional bifurcation diagrams and extracted the effective domains of sustained oscillations. The model includes a calcium balance due to the fundamental importance of calcium influx as proved by simultaneous electrophysiological and calcium imaging procedure. Although there are significant evidences to suggest a partially electrogenic calcium pump, all previous models considered only elecrtogenic pumps. We investigated the effect of the electrogenic calcium pump on the bifurcation diagram of the model and compared our findings against the experimental results.

  6. 2 types of spicules "observed" in 3D realistic models

    CERN Document Server

    Martínez-Sykora, Juan

    2010-01-01

    Realistic numerical 3D models of the outer solar atmosphere show two different kind of spicule-like phenomena, as also observed on the solar limb. The numerical models are calculated using the 2 types of spicules "observed" in 3D realistic models Oslo Staggered Code (OSC) to solve the full MHD equations with non-grey and NLTE radiative transfer and thermal conduction along the magnetic field lines. The two types of spicules arise as a natural result of the dynamical evolution in the models. We discuss the different properties of these two types of spicules, their differences from observed spicules and what needs to be improved in the models.

  7. Realistic Real World Contexts: Model Eliciting Activities

    Science.gov (United States)

    Doruk, Bekir Kürsat

    2016-01-01

    Researchers have proposed a variety of methods to make a connection between real life and mathematics so that it can be learned in a practical way and enable people to utilise mathematics in their daily lives. Model-eliciting activities (MEAs) were developed to fulfil this need and are very capable of serving this purpose. The reason MEAs are so…

  8. Towards Realistic Modeling of Massive Star Clusters

    Science.gov (United States)

    Gnedin, O.; Li, H.

    2016-06-01

    Cosmological simulations of galaxy formation are rapidly advancing towards smaller scales. Current models can now resolve giant molecular clouds in galaxies and predict basic properties of star clusters forming within them. I will describe new theoretical simulations of the formation of the Milky Way throughout cosmic time, with the adaptive mesh refinement code ART. However, many challenges - physical and numerical - still remain. I will discuss how observations of massive star clusters and star forming regions can help us overcome some of them. Video of the talk is available at https://goo.gl/ZoZOfX

  9. Realistic modeling of neurons and networks: towards brain simulation.

    Science.gov (United States)

    D'Angelo, Egidio; Solinas, Sergio; Garrido, Jesus; Casellato, Claudia; Pedrocchi, Alessandra; Mapelli, Jonathan; Gandolfi, Daniela; Prestori, Francesca

    2013-01-01

    Realistic modeling is a new advanced methodology for investigating brain functions. Realistic modeling is based on a detailed biophysical description of neurons and synapses, which can be integrated into microcircuits. The latter can, in turn, be further integrated to form large-scale brain networks and eventually to reconstruct complex brain systems. Here we provide a review of the realistic simulation strategy and use the cerebellar network as an example. This network has been carefully investigated at molecular and cellular level and has been the object of intense theoretical investigation. The cerebellum is thought to lie at the core of the forward controller operations of the brain and to implement timing and sensory prediction functions. The cerebellum is well described and provides a challenging field in which one of the most advanced realistic microcircuit models has been generated. We illustrate how these models can be elaborated and embedded into robotic control systems to gain insight into how the cellular properties of cerebellar neurons emerge in integrated behaviors. Realistic network modeling opens up new perspectives for the investigation of brain pathologies and for the neurorobotic field.

  10. [Realistic surgical training. The Aachen model].

    Science.gov (United States)

    Krones, C J; Binnebösel, M; Stumpf, M; Schumpelick, V

    2010-01-01

    The Aachen model is a practical mode in teaching and advanced training, which is closely geared to the areas of academic acquisition and training. During medical education optional student courses with constitutive curricula offer practical points of contact to the surgical department at all times. Besides improvement of manual training the aims are enhancing interests and acquisition of talents. This guided structure will be intensified with progression into advanced education. Next to the formal guidelines of the curriculum, education logbook and progression conversations, quality, transparency and reliability are particularly emphasized. An evaluation of both the reforms and the surgical trainers is still to be made. In addition procurement of an affirmative occupational image is essential.

  11. Shock Position Control for Mode Transition in a Turbine Based Combined Cycle Engine Inlet Model

    Science.gov (United States)

    Csank, Jeffrey T.; Stueber, Thomas J.

    2013-01-01

    A dual flow-path inlet for a turbine based combined cycle (TBCC) propulsion system is to be tested in order to evaluate methodologies for performing a controlled inlet mode transition. Prior to experimental testing, simulation models are used to test, debug, and validate potential control algorithms which are designed to maintain shock position during inlet disturbances. One simulation package being used for testing is the High Mach Transient Engine Cycle Code simulation, known as HiTECC. This paper discusses the development of a mode transition schedule for the HiTECC simulation that is analogous to the development of inlet performance maps. Inlet performance maps, derived through experimental means, describe the performance and operability of the inlet as the splitter closes, switching power production from the turbine engine to the Dual Mode Scram Jet. With knowledge of the operability and performance tradeoffs, a closed loop system can be designed to optimize the performance of the inlet. This paper demonstrates the design of the closed loop control system and benefit with the implementation of a Proportional-Integral controller, an H-Infinity based controller, and a disturbance observer based controller; all of which avoid inlet unstart during a mode transition with a simulated disturbance that would lead to inlet unstart without closed loop control.

  12. A Dynamic Process Model for the Beach-Inlet Transition Zone.

    Science.gov (United States)

    1980-05-01

    A0-A87 096 UNIVERSITY OF SOUTH FLORIDA TAMPA DEPT OF GEOLOGY F/S 8/3 A DYNAMIC PROCESS MODEL FOR THE REACH-INLET TRANSITION ZONE. UI N MAY 80 R A...cz80 7 A DYNAMIC PROCESS MODEL FOR THE BEACH-INLET TRANSITION ZONE by Richard A. Davis, Jr., University of South Florida and William T. Fox, Williams...during the study period have permitted construction of a dynami, process model for the beach-inlet transition zone during the tidal cycle. This model

  13. An Overview of Westinghouse Realistic Large Break LOCA Evaluation Model

    Directory of Open Access Journals (Sweden)

    Cesare Frepoli

    2008-01-01

    Full Text Available Since the 1988 amendment of the 10 CFR 50.46 rule in 1988, Westinghouse has been developing and applying realistic or best-estimate methods to perform LOCA safety analyses. A realistic analysis requires the execution of various realistic LOCA transient simulations where the effect of both model and input uncertainties are ranged and propagated throughout the transients. The outcome is typically a range of results with associated probabilities. The thermal/hydraulic code is the engine of the methodology but a procedure is developed to assess the code and determine its biases and uncertainties. In addition, inputs to the simulation are also affected by uncertainty and these uncertainties are incorporated into the process. Several approaches have been proposed and applied in the industry in the framework of best-estimate methods. Most of the implementations, including Westinghouse, follow the Code Scaling, Applicability and Uncertainty (CSAU methodology. Westinghouse methodology is based on the use of the WCOBRA/TRAC thermal-hydraulic code. The paper starts with an overview of the regulations and its interpretation in the context of realistic analysis. The CSAU roadmap is reviewed in the context of its implementation in the Westinghouse evaluation model. An overview of the code (WCOBRA/TRAC and methodology is provided. Finally, the recent evolution to nonparametric statistics in the current edition of the W methodology is discussed. Sample results of a typical large break LOCA analysis for a PWR are provided.

  14. Passage Key Inlet, Florida; CMS Modeling and Borrow Site Impact Analysis

    Science.gov (United States)

    2016-06-01

    use of a nested Coastal Modeling System (CMS) model for Passage Key Inlet, which is one of the connections between the Gulf of Mexico and Tampa Bay...XIV-51 June 2016 2 Figure 1. Active USACE Jacksonville District (SAJ) projects in Pinellas, Manatee, and Sarasota Counties, FL. METHOD : The CMS...is a product of the Coastal Inlets Research Program (http://cirp.usace.army.mil) managed at ERDC. CMS is composed of two models, CMS-Flow (Buttolph

  15. Modeling of biofuel pellets torrefaction in a realistic geometry

    Directory of Open Access Journals (Sweden)

    Artiukhina Ekaterina

    2016-01-01

    Full Text Available Low temperature pyrolysis also known as torrefaction is considered as a promising pretreatment technology for conversion of biomass into a solid biofuel with enhanced properties in terms of lower moisture and volatile matter content, hydrophobicity and increased heating value. A thermal treatment leads to a non-uniform temperature field and chemical reactions proceeding unevenly within the pellets. However the temperature is assumed to be uniform in the pellets in the majority of models. Here we report on the model of single pellet biomass torrefaction, taking into account the heat transfer and chemical kinetics in the realistic geometry. The evolution of temperature and material density in the non-stationary thermo-chemical process is described by the system of non-linear partial differential equations. The model describing the high-temperature drying of biomass pellet was also introduced. The importance of boundary effects in realistic simulations of biomass pellets torrefaction is underlined in this work.

  16. Applying a realistic evaluation model to occupational safety interventions

    DEFF Research Database (Denmark)

    Pedersen, Louise Møller

    2017-01-01

    of occupational safety interventions. Conclusion: The revised realistic evaluation model can help safety science forward in identifying key factors for the success of occupational safety interventions. However, future research should strengthen the link between the immediate intervention results and outcome.......Background: Recent literature characterizes occupational safety interventions as complex social activities, applied in complex and dynamic social systems. Hence, the actual outcomes of an intervention will vary, depending on the intervention, the implementation process, context, personal...... characteristics of key actors (defined mechanisms), and the interplay between them, and can be categorized as expected or unexpected. However, little is known about ’how’ to include context and mechanisms in evaluations of intervention effectiveness. A revised realistic evaluation model has been introduced...

  17. Boussinesq Modeling for Inlets, Harbors & Structures (Bouss-2D)

    Science.gov (United States)

    2014-10-27

    longshore and rip currents, wave-current and wave interaction with porous media , wave propagation over vegetated areas, wetlands and marshes, and vessel...circulation in surf and swash zone; wave-current interaction in channels and inlets; generation and impacts of infra- gravity waves on ports and...New structures will be proposed to reduce navigation channel shoaling and decrease vessel influence (e.g., waves, erosion). Ship-to-ship and ship

  18. Toward the classification of the realistic free fermionic models

    Energy Technology Data Exchange (ETDEWEB)

    Faraggi, A.E.

    1997-08-01

    The realistic free fermionic models have had remarkable success in providing plausible explanations for various properties of the Standard Model which include the natural appearance of three generations, the explanation of the heavy top quark mass and the qualitative structure of the fermion mass spectrum in general, the stability of the proton and more. These intriguing achievements makes evident the need to understand the general space of these models. While the number of possibilities is large, general patterns can be extracted. In this paper the author presents a detailed discussion on the construction of the realistic free fermionic models with the aim of providing some insight into the basic structures and building blocks that enter the construction. The role of free phases in the determination of the phenomenology of the models is discussed in detail. The author discusses the connection between the free phases and mirror symmetry in (2,2) models and the corresponding symmetries in the case of (2,0) models. The importance of the free phases in determining the effective low energy phenomenology is illustrated in several examples. The classification of the models in terms of boundary condition selection rules, real world-sheet fermion pairings, exotic matter states and the hidden sector is discussed.

  19. Finite Time Blowup in a Realistic Food-Chain Model

    KAUST Repository

    Parshad, Rana

    2013-05-19

    We investigate a realistic three-species food-chain model, with generalist top predator. The model based on a modified version of the Leslie-Gower scheme incorporates mutual interference in all the three populations and generalizes several other known models in the ecological literature. We show that the model exhibits finite time blowup in certain parameter range and for large enough initial data. This result implies that finite time blowup is possible in a large class of such three-species food-chain models. We propose a modification to the model and prove that the modified model has globally existing classical solutions, as well as a global attractor. We reconstruct the attractor using nonlinear time series analysis and show that it pssesses rich dynamics, including chaos in certain parameter regime, whilst avoiding blowup in any parameter regime. We also provide estimates on its fractal dimension as well as provide numerical simulations to visualise the spatiotemporal chaos.

  20. Assumptions behind size-based ecosystem models are realistic

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Blanchard, Julia L.; Fulton, Elizabeth A.;

    2016-01-01

    A recent publication about balanced harvesting (Froese et al., ICES Journal of Marine Science; doi:10.1093/icesjms/fsv122) contains several erroneous statements about size-spectrum models. We refute the statements by showing that the assumptions pertaining to size-spectrum models discussed...... by Froese et al. are realistic and consistent. We further show that the assumption about density-dependence being described by a stock recruitment relationship is responsible for determining whether a peak in the cohort biomass of a population occurs late or early in life. Finally, we argue...

  1. The KM phase in semi-realistic heterotic orbifold models

    Energy Technology Data Exchange (ETDEWEB)

    Giedt, Joel

    2000-07-05

    In string-inspired semi-realistic heterotic orbifolds models with an anomalous U(1){sub X},a nonzero Kobayashi-Masakawa (KM) phase is shown to arise generically from the expectation values of complex scalar fields, which appear in nonrenormalizable quark mass couplings. Modular covariant nonrenormalizable superpotential couplings are constructed. A toy Z{sub 3} orbifold model is analyzed in some detail. Modular symmetries and orbifold selection rules are taken into account and do not lead to a cancellation of the KM phase. We also discuss attempts to obtain the KM phase solely from renormalizable interactions.

  2. Modeling of Transmembrane Potential in Realistic Multicellular Structures before Electroporation.

    Science.gov (United States)

    Murovec, Tomo; Sweeney, Daniel C; Latouche, Eduardo; Davalos, Rafael V; Brosseau, Christian

    2016-11-15

    Many approaches for studying the transmembrane potential (TMP) induced during the treatment of biological cells with pulsed electric fields have been reported. From the simple analytical models to more complex numerical models requiring significant computational resources, a gamut of methods have been used to recapitulate multicellular environments in silico. Cells have been modeled as simple shapes in two dimensions as well as more complex geometries attempting to replicate realistic cell shapes. In this study, we describe a method for extracting realistic cell morphologies from fluorescence microscopy images to generate the piecewise continuous mesh used to develop a finite element model in two dimensions. The preelectroporation TMP induced in tightly packed cells is analyzed for two sets of pulse parameters inspired by clinical irreversible electroporation treatments. We show that high-frequency bipolar pulse trains are better, and more homogeneously raise the TMP of tightly packed cells to a simulated electroporation threshold than conventional irreversible electroporation pulse trains, at the expense of larger applied potentials. Our results demonstrate the viability of our method and emphasize the importance of considering multicellular effects in the numerical models used for studying the response of biological tissues exposed to electric fields. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. Time variability of α from realistic models of Oklo reactors

    Science.gov (United States)

    Gould, C. R.; Sharapov, E. I.; Lamoreaux, S. K.

    2006-08-01

    We reanalyze Oklo Sm149 data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of α, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the Sm149 effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient Sm149 effective cross sections and use these values to set limits on the time variation of α. Our study resolves a contradictory situation with previous Oklo α results. Our suggested 2σ bound on a possible time variation of α over 2 billion years is stringent: -0.11≤Δα/α≤0.24, in units of 10-7, but model dependent in that it assumes only α has varied over time.

  4. Towards Modeling Realistic Mobility for Performance Evaluations in MANET

    Science.gov (United States)

    Aravind, Alex; Tahir, Hassan

    Simulation modeling plays crucial role in conducting research on complex dynamic systems like mobile ad hoc networks and often the only way. Simulation has been successfully applied in MANET for more than two decades. In several recent studies, it is observed that the credibility of the simulation results in the field has decreased while the use of simulation has steadily increased. Part of this credibility crisis has been attributed to the simulation of mobility of the nodes in the system. Mobility has such a fundamental influence on the behavior and performance of mobile ad hoc networks. Accurate modeling and knowledge of mobility of the nodes in the system is not only helpful but also essential for the understanding and interpretation of the performance of the system under study. Several ideas, mostly in isolation, have been proposed in the literature to infuse realism in the mobility of nodes. In this paper, we attempt a holistic analysis of creating realistic mobility models and then demonstrate creation and analysis of realistic mobility models using a software tool we have developed. Using our software tool, desired mobility of the nodes in the system can be specified, generated, analyzed, and then the trace can be exported to be used in the performance studies of proposed algorithms or systems.

  5. ROC Analysis and a Realistic Model of Heart Rate Variability

    CERN Document Server

    Thurner, S; Teich, M C; Thurner, Stefan; Feurstein, Markus C.; Teich, Malvin C.

    1998-01-01

    We have carried out a pilot study on a standard collection of electrocardiograms from patients who suffer from congestive heart failure, and subjects without cardiac pathology, using receiver-operating-characteristic (ROC) analysis. The scale-dependent wavelet-coefficient standard deviation superior to two commonly used measures of cardiac dysfunction when the two classes of patients cannot be completely separated. A jittered integrate-and-fire model with a fractal Gaussian-noise kernel provides a realistic simulation of heartbeat sequences for both heart-failure patients and normal subjects.

  6. Towards a Realistic Model for Failure Propagation in Interdependent Networks

    CERN Document Server

    Sturaro, Agostino; Conti, Mauro; Das, Sajal K

    2015-01-01

    Modern networks are becoming increasingly interdependent. As a prominent example, the smart grid is an electrical grid controlled through a communications network, which in turn is powered by the electrical grid. Such interdependencies create new vulnerabilities and make these networks more susceptible to failures. In particular, failures can easily spread across these networks due to their interdependencies, possibly causing cascade effects with a devastating impact on their functionalities. In this paper we focus on the interdependence between the power grid and the communications network, and propose a novel realistic model, HINT (Heterogeneous Interdependent NeTworks), to study the evolution of cascading failures. Our model takes into account the heterogeneity of such networks as well as their complex interdependencies. We compare HINT with previously proposed models both on synthetic and real network topologies. Experimental results show that existing models oversimplify the failure evolution and network...

  7. Realistic Mobility Modeling for Vehicular Ad Hoc Networks

    Science.gov (United States)

    Akay, Hilal; Tugcu, Tuna

    2009-08-01

    Simulations used for evaluating the performance of routing protocols for Vehicular Ad Hoc Networks (VANET) are mostly based on random mobility and fail to consider individual behaviors of the vehicles. Unrealistic assumptions about mobility produce misleading results about the behavior of routing protocols in real deployments. In this paper, a realistic mobility modeling tool, Mobility for Vehicles (MOVE), which considers the basic mobility behaviors of vehicles, is proposed for a more accurate evaluation. The proposed model is tested against the Random Waypoint (RWP) model using AODV and OLSR protocols. The results show that the mobility model significantly affects the number of nodes within the transmission range of a node, the volume of control traffic, and the number of collisions. It is shown that number of intersections, grid size, and node density are important parameters when dealing with VANET performance.

  8. Electron percolation in realistic models of carbon nanotube networks

    Science.gov (United States)

    Simoneau, Louis-Philippe; Villeneuve, Jérémie; Rochefort, Alain

    2015-09-01

    The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.

  9. Modeling and Analysis of Realistic Fire Scenarios in Spacecraft

    Science.gov (United States)

    Brooker, J. E.; Dietrich, D. L.; Gokoglu, S. A.; Urban, D. L.; Ruff, G. A.

    2015-01-01

    An accidental fire inside a spacecraft is an unlikely, but very real emergency situation that can easily have dire consequences. While much has been learned over the past 25+ years of dedicated research on flame behavior in microgravity, a quantitative understanding of the initiation, spread, detection and extinguishment of a realistic fire aboard a spacecraft is lacking. Virtually all combustion experiments in microgravity have been small-scale, by necessity (hardware limitations in ground-based facilities and safety concerns in space-based facilities). Large-scale, realistic fire experiments are unlikely for the foreseeable future (unlike in terrestrial situations). Therefore, NASA will have to rely on scale modeling, extrapolation of small-scale experiments and detailed numerical modeling to provide the data necessary for vehicle and safety system design. This paper presents the results of parallel efforts to better model the initiation, spread, detection and extinguishment of fires aboard spacecraft. The first is a detailed numerical model using the freely available Fire Dynamics Simulator (FDS). FDS is a CFD code that numerically solves a large eddy simulation form of the Navier-Stokes equations. FDS provides a detailed treatment of the smoke and energy transport from a fire. The simulations provide a wealth of information, but are computationally intensive and not suitable for parametric studies where the detailed treatment of the mass and energy transport are unnecessary. The second path extends a model previously documented at ICES meetings that attempted to predict maximum survivable fires aboard space-craft. This one-dimensional model implies the heat and mass transfer as well as toxic species production from a fire. These simplifications result in a code that is faster and more suitable for parametric studies (having already been used to help in the hatch design of the Multi-Purpose Crew Vehicle, MPCV).

  10. Supersymmetry and Light Quark Masses in a Realistic Superstring Model

    CERN Document Server

    Halyo, E

    1994-01-01

    We examine the light quark masses in a standard--like superstring model in the four dimensional free fermionic formulation. We find that the supersymmetry constraints in the observable and hidden sectors eliminate all large contributions to $m_u$ and $m_d$ and force them to be much smaller than the other quark masses. The requirement for an acceptable Higgs doublet spectrum results in $m_u<models a realistic $m_d$ can always be obtained whereas $m_u$ is at most $10^{-5}~MeV$. For particular choices of flat directions or vacua $m_u$ can be as small as $10^{-7}~MeV$ but cannot vanish.

  11. Numerical modelling to assess maintenance strategy management options for a small tidal inlet

    Science.gov (United States)

    Shaeri, Saeed; Tomlinson, Rodger; Etemad-Shahidi, Amir; Strauss, Darrell

    2017-03-01

    Small tidal inlets are found to be more sensitive to anthropogenic alteration than their larger counterparts. Such alterations, although typically supported by technical design reports, sometimes require amendments or modification. One of the most suitable tools to conduct the necessary studies in this regard is numerical modelling, since the behaviour of the inlet system in response to proposed remedial actions, can easily be identified. In this paper, various alternative proposals are investigated to determine the most practical and viable option to mitigate the need for ongoing maintenance at a typical small, jettied tidal inlet. The main tool to investigate the alternatives is the hydro-sedimentological modelling of the inlet system, which was performed using the Delft3D software package. The proposed alternative entrance modifications were based upon structural alterations of the inlet system (such as a jetty extension or submerged weir) and non-structural scenarios (such as a change of the time of the dredging campaign or the deposition location of the dredged material). It was concluded that whilst a detailed study is inevitable in order to achieve a comprehensive design plan, based upon the results of this study the construction of a submerged weir at the entrance channel can satisfy the needs of most of the stakeholders, with justifiable costs over a longer period.

  12. Realistic shell model; 132Sn region; 208Pb region

    CERN Document Server

    Covello, A; Gargano, A; Itaco, N

    2008-01-01

    We report on a study of exotic nuclei around doubly magic 132Sn in terms of the shell model employing a realistic effective interaction derived from the CD-Bonn nucleon-nucleon potential. The short-range repulsion of the latter is renormalized by constructing a smooth low-momentum potential, V-low-k, that is used directly as input for the calculation of the effective interaction. In this paper, we focus attention on proton-neutron multiplets in the odd-odd nuclei 134Sb, 136Sb. We show that the behavior of these multiplets is quite similar to that of the analogous multiplets in the counterpart nuclei in the 208Pb region, 210Bi and 212Bi.

  13. Electron distribution in polar heterojunctions within a realistic model

    Energy Technology Data Exchange (ETDEWEB)

    Tien, Nguyen Thanh, E-mail: thanhtienctu@gmail.com [College of Natural Science, Can Tho University, 3-2 Road, Can Tho City (Viet Nam); Thao, Dinh Nhu [Center for Theoretical and Computational Physics, College of Education, Hue University, 34 Le Loi Street, Hue City (Viet Nam); Thao, Pham Thi Bich [College of Natural Science, Can Tho University, 3-2 Road, Can Tho City (Viet Nam); Quang, Doan Nhat [Institute of Physics, Vietnamese Academy of Science and Technology, 10 Dao Tan Street, Hanoi (Viet Nam)

    2015-12-15

    We present a theoretical study of the electron distribution, i.e., two-dimensional electron gas (2DEG) in polar heterojunctions (HJs) within a realistic model. The 2DEG is confined along the growth direction by a triangular quantum well with a finite potential barrier and a bent band figured by all confinement sources. Therein, interface polarization charges take a double role: they induce a confining potential and, furthermore, they can make some change in other confinements, e.g., in the Hartree potential from ionized impurities and 2DEG. Confinement by positive interface polarization charges is necessary for the ground state of 2DEG existing at a high sheet density. The 2DEG bulk density is found to be increased in the barrier, so that the scattering occurring in this layer (from interface polarization charges and alloy disorder) becomes paramount in a polar modulation-doped HJ.

  14. Electron distribution in polar heterojunctions within a realistic model

    Science.gov (United States)

    Tien, Nguyen Thanh; Thao, Dinh Nhu; Thao, Pham Thi Bich; Quang, Doan Nhat

    2015-12-01

    We present a theoretical study of the electron distribution, i.e., two-dimensional electron gas (2DEG) in polar heterojunctions (HJs) within a realistic model. The 2DEG is confined along the growth direction by a triangular quantum well with a finite potential barrier and a bent band figured by all confinement sources. Therein, interface polarization charges take a double role: they induce a confining potential and, furthermore, they can make some change in other confinements, e.g., in the Hartree potential from ionized impurities and 2DEG. Confinement by positive interface polarization charges is necessary for the ground state of 2DEG existing at a high sheet density. The 2DEG bulk density is found to be increased in the barrier, so that the scattering occurring in this layer (from interface polarization charges and alloy disorder) becomes paramount in a polar modulation-doped HJ.

  15. Unsteady velocity measurements in a realistic intracranial aneurysm model

    Science.gov (United States)

    Ugron, Ádám; Farinas, Marie-Isabelle; Kiss, László; Paál, György

    2012-01-01

    The initiation, growth and rupture of intracranial aneurysms are intensively studied by computational fluid dynamics. To gain confidence in the results of numerical simulations, validation of the results is necessary. To this end the unsteady flow was measured in a silicone phantom of a realistic intracranial aneurysm. A flow circuit was built with a novel unsteady flow rate generating method, used to model the idealised shape of the heartbeat. This allowed the measurement of the complex three-dimensional velocity distribution by means of laser-optical methods such as laser doppler anemometry (LDA) and particle image velocimetry (PIV). The PIV measurements, available with high temporal and spatial distribution, were found to have good agreement with the control LDA measurements. Furthermore, excellent agreement was found with the numerical results.

  16. Experimental Study of Aerosol Deposition in a Realistic Lung Model

    Directory of Open Access Journals (Sweden)

    František LÍZAL

    2010-12-01

    Full Text Available The inhalation route for administration of medicaments is becoming more and more popular in recent years. The reason is non-invasiveness of the method and instantaneous absorption of drugs to the blood circulation. It is necessary to deliver exact amount of drug to the specific segment because of occurrence of diverse diseases in different segments of lungs. The aim of our work is to contribute to better understanding of transport and deposition of aerosolized drugs in lungs and hence to more effective treatment of respiratory diseases due to the targeted drug delivery. We provided measurements of aerosol deposition in segmented realistic model of lungs without a mouth cavity. Monodisperse particles marked with fluorescein were supplied to the model. The model was then disassembled to segments and each segment was rinsed with isopropanol, whereby fluorescent samples were created. Each sample was analysed by fluorometer and an amount of aerosol deposited in the segment was calculated. Experiences obtained by this study were used for creation of a new model with the mouth cavity. This model will be used for future studies with porous and fiber aerosols.

  17. Advanced Shock Position Control for Mode Transition in a Turbine Based Combined Cycle Engine Inlet Model

    Science.gov (United States)

    Csank, Jeffrey T.; Stueber, Thomas J.

    2013-01-01

    A dual flow-path inlet system is being tested to evaluate methodologies for a Turbine Based Combined Cycle (TBCC) propulsion system to perform a controlled inlet mode transition. Prior to experimental testing, simulation models are used to test, debug, and validate potential control algorithms. One simulation package being used for testing is the High Mach Transient Engine Cycle Code simulation, known as HiTECC. This paper discusses the closed loop control system, which utilizes a shock location sensor to improve inlet performance and operability. Even though the shock location feedback has a coarse resolution, the feedback allows for a reduction in steady state error and, in some cases, better performance than with previous proposed pressure ratio based methods. This paper demonstrates the design and benefit with the implementation of a proportional-integral controller, an H-Infinity based controller, and a disturbance observer based controller.

  18. Modeling and numerical investigation of the inlet circumferential fluctuations of swept and bowed blades

    Science.gov (United States)

    Tang, Mingzhi; Jin, Donghai; Gui, Xingmin

    2017-02-01

    The circumferential fluctuation (CF) source terms induced by the inviscid blade force can affect the inlet distribution of flow parameters and radial equilibrium of swept and bowed blades. However, these phenomena cannot be adequately described by throughflow methods based on the axisymmetric assumption. A transport model for the CF stresses is proposed and correlated to the distribution of circulation to reflect the effect of the inviscid blade force. To investigate the effect of the inlet CFs on swept and bowed blades, the model is integrated into a throughflow model and applied to a series of cascades with different sweep and bow angles. For swept cascades, the CF source terms change the distributions of incidence angles, as well as the radial equilibrium at the inlet of the blade passage. And the influence is enhanced as the absolute value of the sweep angle increases. For bowed cascades, the distributions of incidence angles are also altered. For both cases, the model can offer a good prediction of the inlet CF source terms, and prove to exert a better prediction of blade design key parameters such as flow angles.

  19. Improved transcranial magnetic stimulation coil design with realistic head modeling

    Science.gov (United States)

    Crowther, Lawrence; Hadimani, Ravi; Jiles, David

    2013-03-01

    We are investigating Transcranial magnetic stimulation (TMS) as a noninvasive technique based on electromagnetic induction which causes stimulation of the neurons in the brain. TMS can be used as a pain-free alternative to conventional electroconvulsive therapy (ECT) which is still widely implemented for treatment of major depression. Development of improved TMS coils capable of stimulating subcortical regions could also allow TMS to replace invasive deep brain stimulation (DBS) which requires surgical implantation of electrodes in the brain. Our new designs allow new applications of the technique to be established for a variety of diagnostic and therapeutic applications of psychiatric disorders and neurological diseases. Calculation of the fields generated inside the head is vital for the use of this method for treatment. In prior work we have implemented a realistic head model, incorporating inhomogeneous tissue structures and electrical conductivities, allowing the site of neuronal activation to be accurately calculated. We will show how we utilize this model in the development of novel TMS coil designs to improve the depth of penetration and localization of stimulation produced by stimulator coils.

  20. Development and validation of a realistic head model for EEG

    Science.gov (United States)

    Bangera, Nitin Bhalchandra

    The utility of extracranial electrical or magnetic field recordings (EEG or MEG) is greatly enhanced if the generators of the bioelectromagnetic fields can be determined accurately from the measured fields. This procedure, known as the 'inverse method,' depends critically on calculations of the projection from generators in the brain to the EEG and MEG sensors. Improving and validating this calculation, known as the 'forward solution,' is the focus of this dissertation. The improvements involve more accurate modeling of the structures of the brain and thus understanding how current flows within the brain as a result of addition of structures in the forward model. Validation compares calculations using different forward models to the experimental results obtained by stimulating with implanted dipole electrodes. The human brain tissue displays inhomogeneity in electrical conductivity and also displays anisotropy, notably in the skull and brain white matter. In this dissertation, a realistic head model has been implemented using the finite element method to calculate the effects of inhomogeneity and anisotropy in the human brain. Accurate segmentation of the brain tissue type is implemented using a semi-automatic method to segment multimodal imaging data from multi-spectral MRI scans (different flip angles) in conjunction with the regular T1-weighted scans and computed x-ray tomography images. The electrical conductivity in the anisotropic white matter tissue is quantified from diffusion tensor MRI. The finite element model is constructed using AMIRA, a commercial segmentation and visualization tool and solved using ABAQUS, a commercial finite element solver. The model is validated using experimental data collected from intracranial stimulation in medically intractable epileptic patients. Depth electrodes are implanted in medically intractable epileptic patients in order to direct surgical therapy when the foci cannot be localized with the scalp EEG. These patients

  1. Realistic Models for Filling Factors in HII Regions

    Science.gov (United States)

    Spangler, Steven R.; Costa, Allison H.; Bergerud, Brandon M.; Beauchamp, Kara M.

    2017-01-01

    One of the parameters used to describe HII regions and other ionized parts of the interstellar medium is the filling factor, defined as the volume fraction of an HII region occupied by matter. The best observational evidence for the existence of a filling factor less than unity is a discrepancy between the electron density derived from density-sensitive line ratios and the root mean square density obtained from emission measure measurements. Following the early, influential study by Osterbrock and Flather (ApJ 129, 26, 1959), most investigations of HII regions envision these objects as a group of isolated cells of high gas density embedded in a vacuum. This picture is at serious odds with more direct measurements of other astrophysical plasmas like the solar wind, where the density follows a less extreme probability distribution function (pdf) such as an exponential or lognormal. We have carried out a set of simulations in which model HII regions are created with different density pdfs such as exponential and lognormal as well as the extreme case of two delta functions. We calculate the electron density as inferred from spectroscopic line ratios and emission measures for all lines of sight through the model nebulas. In the cases of exponential and lognormal pdfs, the spectroscopically derived densities are higher than those obtained by the emission measures by factors of 20 to 100 percent. These are considerably smaller than values often reported in the literature, which can be an order of magnitude or greater. We will discuss possible ways to reconcile realistic density pdfs such as measured in space and laboratory plasmas with the results from astronomical spectroscopic measurements. Finally, we point out that for the Orion Nebula, the density discrepancy is due to geometry, not filling factor (O'Dell, ARAA 39, 99, 2001).

  2. PIV-measured versus CFD-predicted flow dynamics in anatomically realistic cerebral aneurysm models.

    Science.gov (United States)

    Ford, Matthew D; Nikolov, Hristo N; Milner, Jaques S; Lownie, Stephen P; Demont, Edwin M; Kalata, Wojciech; Loth, Francis; Holdsworth, David W; Steinman, David A

    2008-04-01

    Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement

  3. Acoustic mode measurements in the inlet of a model turbofan using a continuously rotating rake

    Science.gov (United States)

    Heidelberg, Laurence J.; Hall, David G.

    1993-01-01

    Comprehensive measurements of the spinning acoustic mode structure in the inlet of the Advanced Ducted Propeller (ADP) have been completed. These measurements were taken using a unique and previously untried method which was first proposed by T.G. Sofrin. A continuously rotating microphone system was employed. The ADP model was designed and built by Pratt & Whitney and tested in the NASA Lewis 9- by 15-foot Anechoic Wind Tunnel. Three inlet configurations were tested with cut-on and cutoff stator vane sets. The cutoff stator was designed to suppress all modes at the blade passing frequency. Rotating rake measurements indicate that several extraneous circumferential modes were active. The mode orders suggest that their source was an interaction between the rotor and small interruptions in the casing tip treatment. The cut-on stator produced the expected circumferential modes plus higher levels of the unexpected modes seen with the cutoff stator.

  4. Comparing Two Numerical Models in Simulating Hydrodynamics and Sediment Transport at a Dual Inlet System, West-Central Florida

    Science.gov (United States)

    2015-05-15

    1 COMPARING TWO NUMERICAL MODELS IN SIMULATING HYDRODYNAMICS AND SEDIMENT TRANSPORT AT A DUAL INLET SYSTEM, WEST-CENTRAL FLORIDA PING WANG1...numerical modeling systems, CMS and DELFT3D, in simulating the hydrodynamic and sediment transport processes. The model results are compared with...Introduction Simulating complex fields of wave, current, sediment transport , and morphology change in the vicinity of tidal inlets is a

  5. Design Optimization of Inlet Plenum of PBMR Using Kriging Modeling Technique

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kwang Yong; Lee, Sang Moon [Mechanical Engineering Department, INHA Univ, Incheon (Korea, Republic of)

    2009-05-15

    In pebble-bed modular reactor (PBMR), the combination of coated particle fuel, inert helium gas as coolant and graphite moderated reactor makes it possible to operate at high temperature yielding a high efficiency. In cooling system of PBMR, Helium gas as the coolant enters the reactor through inlet plenum, i.e., ring channel at the bottom of the reactor, goes up through several rising channels to upper plenum, enters the core at a temperature of about 540 .deg. C and at a pressure of about 7 MPa, and then leaves the reactor through lower plenum at a temperature of about 900 .deg. C under normal operating conditions. Ahmad et al. performed a parametric study on inlet plenum geometry of PBMR with Reynolds-averaged Navier-Stokes (RANS) analysis, and suggested that the flow uniformity in rising channels as well as the pressure drop is found to increase as the channel diameter is decreased. The flow distribution in the rising channels is independent of Reynolds number. Increase in the angle between the inlet ports and aspect ratio is found to increase the uniformity in flow distribution. However, there has not been a trial to introduce systematic optimization techniques in the design of cooling passages of HTGR to find the geometry which maximizes the performance. In this work, shape optimization of inlet plenum and rising channels in PBMR has been performed based on three-dimensional RANS analysis. Kriging model is used as a surrogate model for optimization. The objectives of the design are to maximize the uniformity in the flow distribution in rising channels and to minimize the pressure drop.

  6. Evolution of supersonic corner vortex in a hypersonic inlet/isolator model

    Science.gov (United States)

    Huang, He-Xia; Tan, Hui-Jun; Sun, Shu; Ling, Yu

    2016-12-01

    There are complex corner vortex flows in a rectangular hypersonic inlet/isolator. The corner vortex propagates downstream and interacts with the shocks and expansion waves in the isolator repeatedly. The supersonic corner vortex in a generic hypersonic inlet/isolator model is theoretically and numerically analyzed at a freestream Mach number of 4.92. The cross-flow topology of the corner vortex flow is found to obey Zhang's theory ["Analytical analysis of subsonic and supersonic vortex formation," Acta Aerodyn. Sin. 13, 259-264 (1995)] strictly, except for the short process with the vortex core situated in a subsonic flow which is surrounded by a supersonic flow. In general, the evolution history of the corner vortex under the influence of the background waves in the hypersonic inlet/isolator model can be classified into two types, namely, from the adverse pressure gradient region to the favorable pressure gradient region and the reversed one. For type 1, the corner vortex is a one-celled vortex with the cross-sectional streamlines spiraling inwards at first. Then the Hopf bifurcation occurs and the streamlines in the outer part of the limit cycle switch to spiraling outwards, yielding a two-celled vortex. The limit cycle shrinks gradually and finally vanishes with the streamlines of the entire corner vortex spiraling outwards. For type 2, the cross-sectional streamlines of the corner vortex spiral outwards first. Then a stable limit cycle is formed, yielding a two-celled vortex. The short-lived limit cycle forces the streamlines in the corner vortex to change the spiraling trends rapidly. Although it is found in this paper that there are some defects on the theoretical proof of the limit cycle, Zhang's theory is proven useful for the prediction and qualitative analysis of the complex corner vortex in a hypersonic inlet/isolator. In addition, three conservation laws inside the limit cycle are obtained.

  7. A Turbine Based Combined Cycle Engine Inlet Model and Mode Transition Simulation Based on HiTECC Tool

    Science.gov (United States)

    Csank, Jeffrey T.; Stueber, Thomas J.

    2012-01-01

    An inlet system is being tested to evaluate methodologies for a turbine based combined cycle propulsion system to perform a controlled inlet mode transition. Prior to wind tunnel based hardware testing of controlled mode transitions, simulation models are used to test, debug, and validate potential control algorithms. One candidate simulation package for this purpose is the High Mach Transient Engine Cycle Code (HiTECC). The HiTECC simulation package models the inlet system, propulsion systems, thermal energy, geometry, nozzle, and fuel systems. This paper discusses the modification and redesign of the simulation package and control system to represent the NASA large-scale inlet model for Combined Cycle Engine mode transition studies, mounted in NASA Glenn s 10- by 10-Foot Supersonic Wind Tunnel. This model will be used for designing and testing candidate control algorithms before implementation.

  8. Performance modeling of industrial gas turbines with inlet air filtration system

    Directory of Open Access Journals (Sweden)

    Samuel O. Effiom

    2015-03-01

    Full Text Available The effect of inlet air filtration on the performance of two industrial gas turbines (GT is presented. Two GTs were modeled similar to GE LM2500+ and Alstom GT13 E2-2012, using TURBOMATCH and chosen to operate at environmental conditions of Usan offshore oilfield and Maiduguri dessert in Nigeria. The inlet pressure recovered (Precov from the selected filters used in Usan offshore, and Maiduguri ranged between 98.36≤Precov≤99.51% and 98.67≤Precov≤99.56% respectively. At reduced inlet Precov by 98.36% (1.66 kPa and, at a temperature above 15 °C (ISA, a reduction of 16.9%, and 7.3% of power output and efficiency was obtained using GT13 E2-2012, while a decrease of 14.8% and 4.7% exist for power output and efficiency with GE LM2500+. In addition, a reduction in mass flow rate of air and fuel under the same condition was between 4.3≤mair≤10.6% and 10.4≤mfuel≤11.5% for GT13 E2-2012 and GE LM2500+, correspondingly. However, the GE LM2500+ was more predisposed to intake pressure drops since it functioned at a higher overall pressure ratio. The results obtained were found worthwhile and could be the basis for filter selection and efficient compressor housing design in the locations concerned.

  9. Modeling, simulation and measurement of radiation exposure using electronic personal dosimeters on realistic and ICRU phantoms

    CERN Document Server

    Fuelle, D

    2003-01-01

    Exposure studies with voxel phantoms were carried out to understand the new personal dose measurand Hp(10) measured by personal dosimeters under realistic wearing conditions. Two simulated realistic voxel phantoms and the dosimeter assembly are described in a first step. Conditions such as photon fluence, radiation field geometry, and photon energy for simulating the external photon fields at the realistic model are specified. Person-related effective doses are calculated to evaluate the personal dose. The relation between measured deep personal dose and effective dose is demonstrated and discussed by means of the simulated response function of the dosimeters at realistic phantoms.

  10. Observations and a linear model of water level in an interconnected inlet-bay system

    Science.gov (United States)

    Aretxabaleta, Alfredo L.; Ganju, Neil K.; Butman, Bradford; Signell, Richard P.

    2017-04-01

    A system of barrier islands and back-barrier bays occurs along southern Long Island, New York, and in many coastal areas worldwide. Characterizing the bay physical response to water level fluctuations is needed to understand flooding during extreme events and evaluate their relation to geomorphological changes. Offshore sea level is one of the main drivers of water level fluctuations in semienclosed back-barrier bays. We analyzed observed water levels (October 2007 to November 2015) and developed analytical models to better understand bay water level along southern Long Island. An increase (˜0.02 m change in 0.17 m amplitude) in the dominant M2 tidal amplitude (containing the largest fraction of the variability) was observed in Great South Bay during mid-2014. The observed changes in both tidal amplitude and bay water level transfer from offshore were related to the dredging of nearby inlets and possibly the changing size of a breach across Fire Island caused by Hurricane Sandy (after December 2012). The bay response was independent of the magnitude of the fluctuations (e.g., storms) at a specific frequency. An analytical model that incorporates bay and inlet dimensions reproduced the observed transfer function in Great South Bay and surrounding areas. The model predicts the transfer function in Moriches and Shinnecock bays where long-term observations were not available. The model is a simplified tool to investigate changes in bay water level and enables the evaluation of future conditions and alternative geomorphological settings.

  11. Observations and a linear model of water level in an interconnected inlet-bay system

    Science.gov (United States)

    Aretxabaleta, Alfredo; Ganju, Neil Kamal; Butman, Bradford; Signell, Richard

    2017-01-01

    A system of barrier islands and back-barrier bays occurs along southern Long Island, New York, and in many coastal areas worldwide. Characterizing the bay physical response to water level fluctuations is needed to understand flooding during extreme events and evaluate their relation to geomorphological changes. Offshore sea level is one of the main drivers of water level fluctuations in semienclosed back-barrier bays. We analyzed observed water levels (October 2007 to November 2015) and developed analytical models to better understand bay water level along southern Long Island. An increase (∼0.02 m change in 0.17 m amplitude) in the dominant M2 tidal amplitude (containing the largest fraction of the variability) was observed in Great South Bay during mid-2014. The observed changes in both tidal amplitude and bay water level transfer from offshore were related to the dredging of nearby inlets and possibly the changing size of a breach across Fire Island caused by Hurricane Sandy (after December 2012). The bay response was independent of the magnitude of the fluctuations (e.g., storms) at a specific frequency. An analytical model that incorporates bay and inlet dimensions reproduced the observed transfer function in Great South Bay and surrounding areas. The model predicts the transfer function in Moriches and Shinnecock bays where long-term observations were not available. The model is a simplified tool to investigate changes in bay water level and enables the evaluation of future conditions and alternative geomorphological settings.

  12. Towards More Realistic Mobility Model in Vehicular Ad Hoc Network

    OpenAIRE

    Dhananjay S. Gaikwad; Mahesh Lagad; Prashant Suryawanshi; Vaibhav Maske

    2012-01-01

    Mobility models or the movement patterns of nodes communicating wirelessely, play a vital role in the simulation-based evaluation of vehicular Ad Hoc Networks (VANETs). Even though recent research has developed models that better corresponds to real world mobility, we still have a limited understanding of the level of the required level of mobility details for modeling and simulating VANETs. In this paper, we propose a new mobility model for VANETs that works on the city area and map the topo...

  13. Wind-tunnel blockage and actuation systems test of a two-dimensional scramjet inlet unstart model at Mach 6

    Science.gov (United States)

    Holland, Scott D.

    1994-01-01

    The present study examines the wind-tunnel blockage and actuation systems effectiveness in starting and forcibly unstarting a two-dimensional scramjet inlet in the NASA Langley 20-Inch Mach 6 Tunnel. The intent of the overall test program is to study (both experimentally and computationally) the dynamics of the inlet unstart; however, prior to the design and fabrication of an expensive, instrumented wind-tunnel model, it was deemed necessary first to examine potential wind-tunnel blockage issues related to model sizing and to examine the adequacy of the actuation systems in accomplishing the start and unstart. The model is equipped with both a moveable cowl and aft plug. Windows in the inlet sidewalls allow limited optical access to the internal shock structure; schlieren video was used to identify inlet start and unstart. A chronology of each actuation sequence is provided in tabular form along with still frames from the schlieren video. A pitot probe monitored the freestream conditions throughout the start/unstart process to determine if there was a blockage effect due to the model start or unstart. Because the purpose of this report is to make the phase I (blockage and actuation systems) data rapidly available to the community, the data is presented largely without analysis of the internal shock interactions or the unstart process. This series of tests indicated that the model was appropriately sized for this facility and identified operability limits required first to allow the inlet to start and second to force the unstart.

  14. Realistic model of compact VLSI FitzHugh-Nagumo oscillators

    Science.gov (United States)

    Cosp, Jordi; Binczak, Stéphane; Madrenas, Jordi; Fernández, Daniel

    2014-02-01

    In this article, we present a compact analogue VLSI implementation of the FitzHugh-Nagumo neuron model, intended to model large-scale, biologically plausible, oscillator networks. As the model requires a series resistor and a parallel capacitor with the inductor, which is the most complex part of the design, it is possible to greatly simplify the active inductor implementation compared to other implementations of this device as typically found in filters by allowing appreciable, but well modelled, nonidealities. We model and obtain the parameters of the inductor nonideal model as an inductance in series with a parasitic resistor and a second order low-pass filter with a large cut-off frequency. Post-layout simulations for a CMOS 0.35 μm double-poly technology using the MOSFET Spice BSIM3v3 model confirm the proper behaviour of the design.

  15. Performance of Modeling wireless networks in realistic environment

    CERN Document Server

    Siraj, M

    2012-01-01

    A wireless network is realized by mobile devices which communicate over radio channels. Since, experiments of real life problem with real devices are very difficult, simulation is used very often. Among many other important properties that have to be defined for simulative experiments, the mobility model and the radio propagation model have to be selected carefully. Both have strong impact on the performance of mobile wireless networks, e.g., the performance of routing protocols varies with these models. There are many mobility and radio propagation models proposed in literature. Each of them was developed with different objectives and is not suited for every physical scenario. The radio propagation models used in common wireless network simulators, in general researcher consider simple radio propagation models and neglect obstacles in the propagation environment. In this paper, we study the performance of wireless networks simulation by consider different Radio propagation models with considering obstacles i...

  16. Comparison of realistic head modeling methods in EEG source imaging - biomed 2010.

    Science.gov (United States)

    Vatta, F; Meneghini, F; Esposito, F; Mininel, S; Disalle, F

    2010-01-01

    EEG inverse source imaging aims at reconstructing the underlying current distribution in the human brain using potential differences measured non-invasively from the head surface. A critical component of source reconstruction is the head volume conductor model used to reach an accurate solution of the associated forward problem, i.e., the simulation of the EEG for a known current source in the brain. The volume conductor model contains both the geometry and the electrical conduction properties of the head tissues and the accuracy of both parameters has direct impact on the accuracy of the source analysis. This was examined in detail with two different human head models. Two realistic head models derived from an averaged T1-weighted MRI dataset of the Montreal Neurological Institute (MNI) were used for this study. These models were: (1) BEM Model: a four-shell surface-based Boundary Elements (BEM) head model; (2) FDM Model: a volume-based Finite Difference (FDM) model, which allows better modeling accuracy than BEM as it better represents the cortical structures, such as, sulci and gyri in the brain in a three-dimensional head model. How model accuracy description influences the EEG source localizations was studied with the above realistic models of the head. We present here a detailed computer simulation study in which the performances of the two realistic four-shell head models are compared, the realistic MNI-based BEM Model and the FDM Model. As figures of merit for the comparative analysis, the point spread function (PSF) maps and the lead field (LF) correlation coefficients are used. The obtained results demonstrate that a better description of realistic geometry can provide a factor of improvement particularly important when considering sources placed in the temporal or in the occipital cortex. In these situations, using a more refined realistic head model will allow a better spatial discrimination of neural sources.

  17. Realistic cosmological model with dynamical cancellation of vacuum energy

    CERN Document Server

    Dolgov, A D

    2003-01-01

    We propose a model with a compensating scalar field whose back reaction to the cosmological curvature cancels possible vacuum energy density down to the terms of the order of the time dependent critical energy density. Thus the model simultaneously solves the mystery of the compensation of vacuum energy with the accuracy of 120 orders of magnitude and explains existence of the observed dark energy. At an early stage the suggested cosmological model might experience exponential expansion without an additional inflaton field.

  18. More-Realistic Digital Modeling of a Human Body

    Science.gov (United States)

    Rogge, Renee

    2010-01-01

    A MATLAB computer program has been written to enable improved (relative to an older program) modeling of a human body for purposes of designing space suits and other hardware with which an astronaut must interact. The older program implements a kinematic model based on traditional anthropometric measurements that do provide important volume and surface information. The present program generates a three-dimensional (3D) whole-body model from 3D body-scan data. The program utilizes thin-plate spline theory to reposition the model without need for additional scans.

  19. A Simplified Model for Generating 3D Realistic Sound in the Multimedia and Virtual Reality Systems

    Institute of Scientific and Technical Information of China (English)

    赵Yu; 何志均; 等

    1996-01-01

    It is a key feature to embed 3D realistic sound effect in the future multimedia and virtual reality systems.Recent research on acoustics and psychoacoustics reveals the important cues for sound localization and sound perception.One promising approach to generate 3D realistic sound effect uses two earphones by simulating the sound waveforms from sound source to eardrum.This paper summarizes two methods for generating 3D realistic sound and points out their inherent drawbacks.To overcome these drawbacks we propose a simplified model to generate 3D realistic sound at any positions in the horizontal plane based on the results of sound perception and localization.Experimental results show that the model is correct and efficient.

  20. A realistic dynamic blower energy consumption model for wastewater applications.

    Science.gov (United States)

    Amerlinck, Y; De Keyser, W; Urchegui, G; Nopens, I

    2016-10-01

    At wastewater treatment plants (WWTPs) aeration is the largest energy consumer. This high energy consumption requires an accurate assessment in view of plant optimization. Despite the ever increasing detail in process models, models for energy production still lack detail to enable a global optimization of WWTPs. A new dynamic model for a more accurate prediction of aeration energy costs in activated sludge systems, equipped with submerged air distributing diffusers (producing coarse or fine bubbles) connected via piping to blowers, has been developed and demonstrated. This paper addresses the model structure, its calibration and application to the WWTP of Mekolalde (Spain). The new model proved to give an accurate prediction of the real energy consumption by the blowers and captures the trends better than the constant average power consumption models currently being used. This enhanced prediction of energy peak demand, which dominates the price setting of energy, illustrates that the dynamic model is preferably used in multi-criteria optimization exercises for minimizing the energy consumption.

  1. Flavor changing neutral currents in a realistic composite technicolor model

    Science.gov (United States)

    Carone, Christopher D.; Hamilton, Rowan T.

    1993-03-01

    We consider the phenomenology of a composite technicolor model proposed recently by Georgi. Composite technicolor interactions produce four-quark operators in the low energy theory that contribute to flavor changing neutral current processes. While we expect operators of this type to be induced at the compositeness scale by the flavor-symmetry breaking effects of the preon mass matrices, the Georgi model also includes operators from higher scales that are not GIM-suppressed. Since these operators are potentially large, we study their impact on flavor changing neutral currents and CP violation in the neutral K, B, and D meson systems. Notably, we find that this model gives rise to a typical value for {ɛ‧}/{ɛ} that is much smaller than most standard model estimates.

  2. A Note on Realistic Dividends in Actuarial Surplus Models

    Directory of Open Access Journals (Sweden)

    Benjamin Avanzi

    2016-10-01

    Full Text Available Because of the profitable nature of risk businesses in the long term, de Finetti suggested that surplus models should allow for cash leakages, as otherwise the surplus would unrealistically grow (on average to infinity. These leakages were interpreted as ‘dividends’. Subsequent literature on actuarial surplus models with dividend distribution has mainly focussed on dividend strategies that either maximise the expected present value of dividends until ruin or lead to a probability of ruin that is less than one (see Albrecher and Thonhauser, Avanzi for reviews. An increasing number of papers are directly interested in modelling dividend policies that are consistent with actual practice in financial markets. In this short note, we review the corporate finance literature with the specific aim of fleshing out properties that dividend strategies should ideally satisfy, if one wants to model behaviour that is consistent with practice.

  3. Comparison of two models of a Double Inlet Miniature Pulse Tube Refrigerator - Part B Electrical Analogy

    CERN Document Server

    Bailly, Y; Bailly, Yannick; Nika, Philippe

    2002-01-01

    The design of a Double Inlet Pulse Tube Refrigerator is investigated by means of an analogy with an electric circuit. The results obtained with the electric scheme are compared with both those of the thermodynamic model (Part A) and experiments. The basic formulation of equivalent electronic components is discussed and a few improvements are proposed to adjust the theoretical expressions of the electrical impedances of capillaries and regenerator in order to consider additional effects such pressure drops due to geometrical singularities at different internal flow regimes. A simplified formulation for the regenerator inefficiency is deduced from considerations on its harmonic functioning. The main purpose of this analysis considers especially the design of miniature cryocoolers dedicated to electronic applications. These models are applied to a commercial miniature refrigerator. A discussion of their relevance is achieved and a few suggestions on the refrigerator design are proposed to improve the cooling pro...

  4. A simple but realistic model for laser cladding

    Energy Technology Data Exchange (ETDEWEB)

    Picasso, M.; Marsden, C.F.; Wagniere, J.D.; Frenk, A.; Rappaz, M. (Ecole Polytechnique Federale de Lausanne (Switzerland))

    1994-04-01

    The steady development of high-power lasers has encouraged the industrial application of laser surface treatments. The aim of the laser-cladding process is to deposit a protective layer (from 0.1 to 1.5 mm) onto a workpiece and for the two to be joined by a fusion bond. A model which takes into account the main phenomena occurring during the laser-cladding process is proposed. For a given laser power, beam radius, powder jet geometry, and clad height, this model evaluates two other processing parameters, namely, the laser-beam velocity and the powder feed rate. It considers the interactions between the powder particles, the laser beam, and the molten pool. The laser power reaching the surface of the workpiece is estimated and, assuming this power is used to remelt the substrate with the clad having been predeposited, the melt-pool shape is computed using a three-dimensional (3-D) analytical model, which produces immediate results, even on personal computers. The predictions obtained with this numerical model are in good agreement with experimental results. Processing engineers may therefore use this model to choose the correct processing parameters and to establish cladding maps.

  5. Model of Ni-63 battery with realistic PIN structure

    Energy Technology Data Exchange (ETDEWEB)

    Munson, Charles E.; Voss, Paul L.; Ougazzaden, Abdallah, E-mail: aougazza@georgiatech-metz.fr [Georgia Tech Lorraine, Georgia Tech-C.N.R.S., UMI2958, 2-3 rue Marconi, 57070 Metz (France); School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive NW, 30332-0250 Atlanta (United States); Arif, Muhammad; Salvestrini, Jean-Paul [Georgia Tech Lorraine, Georgia Tech-C.N.R.S., UMI2958, 2-3 rue Marconi, 57070 Metz (France); Université de Lorraine, CentraleSupélec, LMOPS, EA 4423, 2 rue E. Belin, 57070 Metz (France); Streque, Jeremy; El Gmili, Youssef [Georgia Tech Lorraine, Georgia Tech-C.N.R.S., UMI2958, 2-3 rue Marconi, 57070 Metz (France); Belahsene, Sofiane; Martinez, Anthony; Ramdane, Abderrahim [Laboratory for Photonics and Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis (France)

    2015-09-14

    GaN, with its wide bandgap of 3.4 eV, has emerged as an efficient material for designing high-efficiency betavoltaic batteries. An important part of designing efficient betavoltaic batteries involves a good understanding of the full process, from the behavior of the nuclear material and the creation of electron-hole pairs all the way through the collection of photo-generated carriers. This paper presents a detailed model based on Monte Carlo and Silvaco for a GaN-based betavoltaic battery device, modeled after Ni-63 as an energy source. The accuracy of the model is verified by comparing it with experimental values obtained for a GaN-based p-i-n structure under scanning electron microscope illumination.

  6. Gauge and Matter Condensates in Realistic String Models

    CERN Document Server

    Kalara, S; Pages, D N

    1992-01-01

    We examine the inter-relationship of the superpotential containing hidden and observable matter fields and the ensuing condensates in free fermionic string models. These gauge and matter condensates of the strongly interacting hidden gauge groups play a crucial role in the determination of the physical parameters of the observable sector. Supplementing the above information with the requirement of modular invariance, we find that a generic model with only trilinear superpotential allows for a degenerate (and sometimes pathological) set of vacua. This degeneracy may be lifted by higher order terms in the superpotential. We also point out some other subtle points that may arise in calculations of this nature. We exemplify our observations by computing explicitly the modular invariant gaugino and matter condensates in the flipped $SU(5)$ string model with hidden gauge group $SO(10)\\times SU(4)$.

  7. Flavor Changing Neutral Currents in a Realistic Composite Technicolor Model

    CERN Document Server

    Carone, C D; Carone, Christopher D.; Hamilton, Rowan T.

    1993-01-01

    We consider the phenomenology of a composite technicolor model proposed recently by Georgi. Composite technicolor interactions produce four-quark operators in the low energy theory that contribute to flavor changing neutral current processes. While we expect operators of this type to be induced at the compositeness scale by the flavor-symmetry breaking effects of the preon mass matrices, the Georgi model also includes operators from higher scales that are not GIM-suppressed. Since these operators are potentially large, we study their impact on flavor changing neutral currents and CP violation in the neutral $B$, $D$, and $K$ meson systems.

  8. A Realistic Cellular Automaton Model for Synchronized Traffic Flow

    Institute of Scientific and Technical Information of China (English)

    ZHAO Bo-Han; HU Mao-Bin; JIANG Rui; WU Qing-Song

    2009-01-01

    A cellular automaton model is proposed to consider the anticipation effect in drivers' behavior. It is shown that the anticipation effect can be one of the origins of synchronized traffic flow. With anticipation effect, the congested traffic flow simulated by the model exhibits the features of synchronized flow. The spatiotemporal patterns induced by an on-ramp are also consistent with the three-phaee traffic theory. Since the origin of synchronized flow is still controversial, our work can shed some light on the mechanism of synchronized flow.

  9. Family universal anomalous U(1) in realistic superstring derived models

    Energy Technology Data Exchange (ETDEWEB)

    Faraggi, A.E.

    1998-01-01

    An important issue in supersymmetry phenomenology is the suppression of squarks contributions to Flavor Changing Neutral Currents (FCNC). Recently it was noted that in some free fermionic three generation models the anomalous U(1) is family universal. It was further shown that if the D-term of the U(1){sub A} is the dominant source of supersymmetry breaking, the squark masses are indeed approximately degenerate. In this paper the author discusses the properties of the superstring models that give rise to the flavor universal anomalous U(1). The root cause for the universal U(1){sub A} is the cyclic permutation symmetry, the characteristic property of the Z{sub 2} X Z{sub 2} orbifold compactification, realized in the free fermionic models by the NAHE set of boundary condition basis vectors. The properties of the three generation models that preserve this cyclic permutation symmetry in the flavor charges are discussed. The cyclic permutation symmetry of the Z{sub 2} x Z{sub 2} orbifold compactification is proposed to be the characteristic property, of phenomenological interest, that distinguishes it from other classes of superstring compactifications.

  10. Fast, Automated, Photo realistic, 3D Modeling of Building Interiors

    Science.gov (United States)

    2016-09-12

    These models are used in augmented reality , navigation, and energy simulation applications. State -of- the- art scanning produces accurate pointclouds of...preservation, entertainment, and augmented reality , the demand for both fast and accurate scanning technologies has dramatically increased. In this...With applications such as historical preservation, entertainment, and augmented reality , the demand for both fast and accurate scanning

  11. Shadow obstacle model for realistic corner-turning behavior in crowd simulation

    Institute of Scientific and Technical Information of China (English)

    Gao-qi HE; Yi JIN; Qi CHEN; Zhen LIU; Wen-hui YUE; Xing-jian LU

    2016-01-01

    This paper describes a novel model known as the shadow obstacle model to generate a realistic corner-turning be-havior in crowd simulation. The motivation for this model comes from the observation that people tend to choose a safer route rather than a shorter one when turning a corner. To calculate a safer route, an optimization method is proposed to generate the corner-turning rule that maximizes the viewing range for the agents. By combining psychological and physical forces together, a full crowd simulation framework is established to provide a more realistic crowd simulation. We demonstrate that our model produces a more realistic corner-turning behavior by comparison with real data obtained from the experiments. Finally, we per-form parameter analysis to show the believability of our model through a series of experiments.

  12. Toward the M(F)-theory embedding of realistic free-fermion models

    Energy Technology Data Exchange (ETDEWEB)

    Berglund, P. [Univ. of California, Santa Barbara, CA (United States). Institute for Theoretical Physics; Ellis, J. [CERN, Geneva (Switzerland). Theory Division; Faraggi, A.E. [Univ. of Florida, Gainesville, FL (United States). Institute for Fundamental Theory] [and others

    1998-03-01

    We construct a Landau-Ginzburg model with the same data and symmetries as a Z{sub 2} x Z{sub 2} orbifold that corresponds to a class of realistic free-fermion models. Within the class of interest, we show that this orbifolding connects between different Z{sub 2} x Z{sub 2} orbifold models and connects with the mirror symmetry. Our work suggests that duality symmetries previously discussed in the context of specific M and F theory compactifications may be extended to the special Z{sub 2} x Z{sub 2} orbifold that characterizes realistic free-fermion models.

  13. A new model for realistic random perturbations of stochastic oscillators

    Science.gov (United States)

    Dieci, Luca; Li, Wuchen; Zhou, Haomin

    2016-08-01

    Classical theories predict that solutions of differential equations will leave any neighborhood of a stable limit cycle, if white noise is added to the system. In reality, many engineering systems modeled by second order differential equations, like the van der Pol oscillator, show incredible robustness against noise perturbations, and the perturbed trajectories remain in the neighborhood of a stable limit cycle for all times of practical interest. In this paper, we propose a new model of noise to bridge this apparent discrepancy between theory and practice. Restricting to perturbations from within this new class of noise, we consider stochastic perturbations of second order differential systems that -in the unperturbed case- admit asymptotically stable limit cycles. We show that the perturbed solutions are globally bounded and remain in a tubular neighborhood of the underlying deterministic periodic orbit. We also define stochastic Poincaré map(s), and further derive partial differential equations for the transition density function.

  14. A realistic model for quantum theory with a locality property

    Energy Technology Data Exchange (ETDEWEB)

    Eberhard, P.H.

    1987-04-01

    A model reproducing the predictions of relativistic quantum theory to any desired degree of accuracy is described in this paper. It involves quantities that are independent of the observer's knowledge, and therefore can be called real, and which are defined at each point in space, and therefore can be called local in a rudimentary sense. It involves faster-than-light, but not instantaneous, action at distance.

  15. D-term Spectroscopy in Realistic Heterotic-String Models

    CERN Document Server

    Dedes, Athanasios

    2000-01-01

    The emergence of free fermionic string models with solely the MSSM charged spectrum below the string scale provides further evidence to the assertion that the true string vacuum is connected to the Z_2 x Z_2 orbifold in the vicinity of the free fermionic point in the Narain moduli space. An important property of the Z_2 x Z_2 orbifold is the cyclic permutation symmetry between the three twisted sectors. If preserved in the three generations models the cyclic permutation symmetry results in a family universal anomalous U(1)_A, which is instrumental in explaining squark degeneracy, provided that the dominant component of supersymmetry breaking arises from the U(1)_A D-term. Interestingly, the contribution of the family--universal D_A-term to the squark masses may be intra-family non-universal, and may differ from the usual (universal) boundary conditions assumed in the MSSM. We contemplate how D_A--term spectroscopy may be instrumental in studying superstring models irrespective of our ignorance of the details ...

  16. Realistic Mathematics Learning Using Cooperative Strategy Model in Junior High School

    Science.gov (United States)

    Dwiyana

    2015-01-01

    This study aims to develop a realistic mathematics learning model using cooperative strategy. This study applies research and development approach conducted at Junior High School "Laboratorium," State University of Malang. The implementation of this model is conducted through five stages: 1) previous study phase; 2) model planning phase;…

  17. Realistic modeling of clinical laboratory operation by computer simulation.

    Science.gov (United States)

    Vogt, W; Braun, S L; Hanssmann, F; Liebl, F; Berchtold, G; Blaschke, H; Eckert, M; Hoffmann, G E; Klose, S

    1994-06-01

    An important objective of laboratory management is to adjust the laboratory's capability to the needs of patients' care as well as economy. The consequences of management may be changes in laboratory organization, equipment, or personnel planning. At present only one's individual experience can be used for making such decisions. We have investigated whether the techniques of operations research could be transferred to a clinical laboratory and whether an adequate simulation model of the laboratory could be realized. First we listed and documented the system design and the process flow for each single laboratory request. These input data were linked by the simulation model (programming language SIMSCRIPT II.5). The output data (turnaround times, utilization rates, and analysis of queue length) were validated by comparison with the current performance data obtained by tracking specimen flow. Congruence of the data was excellent (within +/- 4%). In planning experiments we could study the consequences of changes in order entry, staffing, and equipment on turnaround times, utilization, and queue lengths. We conclude that simulation can be a valuable tool for better management decisions.

  18. Realistic Representation of Trees in an Urban Canopy Model

    Science.gov (United States)

    Ryu, Young-Hee; Bou-Zeid, Elie; Wang, Zhi-Hua; Smith, James A.

    2016-05-01

    A single-layer urban canopy model that captures sub-facet heterogeneity and various hydrological processes is further developed to explicitly incorporate trees within the urban canyon. The physical processes associated with trees are shortwave/longwave radiation exchange, including mutual interception and shading by trees and buildings and multiple reflections, sensible heat and latent heat (through transpiration) exchange, and root water uptake. A computationally-efficient geometric approach is applied to the radiation exchanges, requiring a priori knowledge of view factors. These view factors are first obtained from independent Monte Carlo ray-tracing simulations, and subsequently simple relations, which are functions of canyon aspect ratio and tree-crown ratio, are proposed to estimate them. The developed model is evaluated against field observations at two urban sites and one suburban site, showing improved performance for latent heat flux compared to the previous version that only includes ground vegetation. The trees in the urban canopy act to considerably decrease sensible heat flux and increase latent heat flux, and these effects are found to be more significant in the more dense urban site. Sensitivity tests are then performed to examine the effects of tree geometry relative to canyon geometry. The results indicate that the tree-crown size relative to canyon width is the most influential parameter to decrease sensible heat flux and increase latent heat flux, resulting in cooling of the urban area.

  19. Reliable modeling of the electronic spectra of realistic uranium complexes

    Science.gov (United States)

    Tecmer, Paweł; Govind, Niranjan; Kowalski, Karol; de Jong, Wibe A.; Visscher, Lucas

    2013-07-01

    We present an EOMCCSD (equation of motion coupled cluster with singles and doubles) study of excited states of the small [UO2]2+ and [UO2]+ model systems as well as the larger UVIO2(saldien) complex. In addition, the triples contribution within the EOMCCSDT and CR-EOMCCSD(T) (completely renormalized EOMCCSD with non-iterative triples) approaches for the [UO2]2+ and [UO2]+ systems as well as the active-space variant of the CR-EOMCCSD(T) method—CR-EOMCCSd(t)—for the UVIO2(saldien) molecule are investigated. The coupled cluster data were employed as benchmark to choose the "best" appropriate exchange-correlation functional for subsequent time-dependent density functional (TD-DFT) studies on the transition energies for closed-shell species. Furthermore, the influence of the saldien ligands on the electronic structure and excitation energies of the [UO2]+ molecule is discussed. The electronic excitations as well as their oscillator dipole strengths modeled with TD-DFT approach using the CAM-B3LYP exchange-correlation functional for the [UVO2(saldien)]- with explicit inclusion of two dimethyl sulfoxide molecules are in good agreement with the experimental data of Takao et al. [Inorg. Chem. 49, 2349 (2010), 10.1021/ic902225f].

  20. Automatic procedure for realistic 3D finite element modelling of human brain for bioelectromagnetic computations

    Energy Technology Data Exchange (ETDEWEB)

    Aristovich, K Y; Khan, S H, E-mail: kirill.aristovich.1@city.ac.u [School of Engineering and Mathematical Sciences, City University London, Northampton Square, London EC1V 0HB (United Kingdom)

    2010-07-01

    Realistic computer modelling of biological objects requires building of very accurate and realistic computer models based on geometric and material data, type, and accuracy of numerical analyses. This paper presents some of the automatic tools and algorithms that were used to build accurate and realistic 3D finite element (FE) model of whole-brain. These models were used to solve the forward problem in magnetic field tomography (MFT) based on Magnetoencephalography (MEG). The forward problem involves modelling and computation of magnetic fields produced by human brain during cognitive processing. The geometric parameters of the model were obtained from accurate Magnetic Resonance Imaging (MRI) data and the material properties - from those obtained from Diffusion Tensor MRI (DTMRI). The 3D FE models of the brain built using this approach has been shown to be very accurate in terms of both geometric and material properties. The model is stored on the computer in Computer-Aided Parametrical Design (CAD) format. This allows the model to be used in a wide a range of methods of analysis, such as finite element method (FEM), Boundary Element Method (BEM), Monte-Carlo Simulations, etc. The generic model building approach presented here could be used for accurate and realistic modelling of human brain and many other biological objects.

  1. Order Matters: Sequencing Scale-Realistic Versus Simplified Models to Improve Science Learning

    Science.gov (United States)

    Chen, Chen; Schneps, Matthew H.; Sonnert, Gerhard

    2016-10-01

    Teachers choosing between different models to facilitate students' understanding of an abstract system must decide whether to adopt a model that is simplified and striking or one that is realistic and complex. Only recently have instructional technologies enabled teachers and learners to change presentations swiftly and to provide for learning based on multiple models, thus giving rise to questions about the order of presentation. Using disjoint individual growth modeling to examine the learning of astronomical concepts using a simulation of the solar system on tablets for 152 high school students (age 15), the authors detect both a model effect and an order effect in the use of the Orrery, a simplified model that exaggerates the scale relationships, and the True-to-scale, a proportional model that more accurately represents the realistic scale relationships. Specifically, earlier exposure to the simplified model resulted in diminution of the conceptual gain from the subsequent realistic model, but the realistic model did not impede learning from the following simplified model.

  2. Three-nucleon bound states using realistic potential models

    Science.gov (United States)

    Nogga, A.; Kievsky, A.; Kamada, H.; Glöckle, W.; Marcucci, L. E.; Rosati, S.; Viviani, M.

    2003-03-01

    The bound states of 3H and 3He have been calculated by using the Argonne v18 plus the Urbana IX three-nucleon potential. The isospin T=3/2 state have been included in the calculations as well as the n-p mass difference. The 3H-3He mass difference has been evaluated through the charge-dependent terms explicitly included in the two-body potential. The calculations have been performed using two different methods: the solution of the Faddeev equations in momentum space and the expansion on the correlated hyperspherical harmonic basis. The results are in agreement within 0.1% and can be used as benchmark tests. Results for the charge-dependent Bonn interaction in conjunction with the Tucson-Melbourne three-nucleon force are also presented. It is shown that the 3H and 3He binding energy difference can be predicted model independently.

  3. The three-nucleon bound state using realistic potential models

    CERN Document Server

    Nogga, A; Kamada, H; Glöckle, W; Marcucci, L E; Rosati, S; Viviani, M

    2003-01-01

    The bound states of $^3$H and $^3$He have been calculated using the Argonne $v_{18}$ plus the Urbana three-nucleon potential. The isospin $T=3/2$ state have been included in the calculations as well as the $n$-$p$ mass difference. The $^3$H-$^3$He mass difference has been evaluated through the charge dependent terms explicitly included in the two-body potential. The calculations have been performed using two different methods: the solution of the Faddeev equations in momentum space and the expansion on the correlated hyperspherical harmonic basis. The results are in agreement within 0.1% and can be used as benchmark tests. Results for the CD-Bonn interaction are also presented. It is shown that the $^3$H and $^3$He binding energy difference can be predicted model independently.

  4. Influence of atmospheric turbulence on OAM-based FSO system with use of realistic link model

    Science.gov (United States)

    Li, Ming; Yu, Zhongyuan; Cvijetic, Milorad

    2016-04-01

    We study the influence of atmospheric turbulence on OAM-based free-space optical (FSO) communication by using the Pump turbulence spectrum model which accurately characterizes the realistic FSO link. A comprehensive comparison is made between the Pump and Kolmogorov spectrum models with respect to the turbulence impact. The calculated results show that obtained turbulence-induced crosstalk is lower, which means that a higher channel capacity is projected when the realistic Pump spectrum is used instead of the Kolmogorov spectrum. We believe that our results prove that performance of practical OAM-based FSO is better than one predicted by using the original Kolmogorov turbulence model.

  5. Combining Street View and Aerial Images to Create Photo-Realistic 3D City Models

    OpenAIRE

    Ivarsson, Caroline

    2014-01-01

    This thesis evaluates two different approaches of using panoramic street view images for creating more photo-realistic 3D city models comparing to 3D city models based on only aerial images. The thesis work has been carried out at Blom Sweden AB with the use of their software and data. The main purpose of this thesis work has been to investigate if street view images can aid in creating more photo-realistic 3D city models on street level through an automatic or semi-automatic approach. Two di...

  6. Plasticity-modulated seizure dynamics for seizure termination in realistic neuronal models

    NARCIS (Netherlands)

    Koppert, M.M.J.; Kalitzin, S.; Lopes da Silva, F.H.; Viergever, M.A.

    2011-01-01

    In previous studies we showed that autonomous absence seizure generation and termination can be explained by realistic neuronal models eliciting bi-stable dynamics. In these models epileptic seizures are triggered either by external stimuli (reflex epilepsies) or by internal fluctuations. This scena

  7. Plasticity-modulated seizure dynamics for seizure termination in realistic neuronal models

    NARCIS (Netherlands)

    Koppert, M.M.J.; Kalitzin, S.; Lopes da Silva, F.H.; Viergever, M.A.

    2011-01-01

    In previous studies we showed that autonomous absence seizure generation and termination can be explained by realistic neuronal models eliciting bi-stable dynamics. In these models epileptic seizures are triggered either by external stimuli (reflex epilepsies) or by internal fluctuations. This

  8. CERN Proton Synchrotron booster space charge simulations with a realistic model for alignment and field errors*

    Science.gov (United States)

    Forte, V.; Benedetto, E.; McAteer, M.

    2016-12-01

    The CERN Proton Synchrotron booster (PSB) is one of the machines of the LHC injector chain which will be upgraded within the LHC Injectors Upgrade (LIU) project. The injection energy of the PSB will be increased to 160 MeV in order to mitigate direct space charge effects, considered to be the main performance limitation, aiming to double the brightness for the LHC beams. In order to better predict the gain to be expected, space charge simulations are being carried out. As a first step, benchmarking between simulations and measurements is needed. Efforts to establish a realistic modeling of field and alignment errors aim at extending the basic model of the machine toward a more realistic one. Simulations of beam dynamics with strong space charge and realistic errors are presented and analyzed in this paper.

  9. Comparative analysis of realistic CT-scan and simplified human airway models in airflow simulation.

    Science.gov (United States)

    Johari, Nasrul Hadi; Osman, Kahar; Helmi, Nor Harris N; Abdul Kadir, Mohammed A Rafiq

    2015-01-01

    Efforts to model the human upper respiratory system have undergone many phases. Geometrical proximity to the realistic shape has been the subject of many research projects. In this study, three different geometries of the trachea and main bronchus were modelled, which were reconstructed from computed tomography (CT) scan images. The geometrical variations were named realistic, simplified and oversimplified. Realistic refers to the lifelike image taken from digital imaging and communications in medicine format CT scan images, simplified refers to the reconstructed image based on natural images without realistic details pertaining to the rough surfaces, and oversimplified describes the straight wall geometry of the airway. The characteristics of steady state flows with different flow rates were investigated, simulating three varied physical activities and passing through each model. The results agree with previous studies where simplified models are sufficient for providing comparable results for airflow in human airways. This work further suggests that, under most exercise conditions, the idealised oversimplified model is not favourable for simulating either airflow regimes or airflow with particle depositions. However, in terms of immediate analysis for the prediction of abnormalities of various dimensions of human airways, the oversimplified techniques may be used.

  10. Comparison of two models of a double inlet miniature pulse tube refrigerator: Part A thermodynamics

    Science.gov (United States)

    Nika, Philippe; Bailly, Yannick

    2002-10-01

    The cooling of electronic components is of great interest to improve their capabilities, especially for CMOS components or infrared sensors. The purpose of this paper is to present the design and the optimization of a miniature double inlet pulse tube refrigerator (DIPTR) dedicated to such applications. Special precautions have to be considered in modeling the global functioning of small scale DIPTR systems and also in estimating the net cooling power. In fact, thermal gradients are greater than those observed in normal scale systems, and moreover, because of the small dimensions of ducts (diameter), the pulse tube cannot be assumed to be adiabatic. Hence thermal heat conduction phenomena must be considered. Besides dead volumes introduced by junctions and capillaries cannot be neglected any more in front of the volume of the gas tube itself. The hydrodynamic and thermal behaviors of the cooler are predicted by means of two different approaches: a classical thermodynamic model and a model based on an electrical analogy. The results of these analysis are tested and criticized by comparing them with experimental data obtained on a small commercial pulse tube refrigerator.

  11. Cold and hot cognition: quantum probability theory and realistic psychological modeling.

    Science.gov (United States)

    Corr, Philip J

    2013-06-01

    Typically, human decision making is emotionally "hot" and does not conform to "cold" classical probability (CP) theory. As quantum probability (QP) theory emphasises order, context, superimposition states, and nonlinear dynamic effects, one of its major strengths may be its power to unify formal modeling and realistic psychological theory (e.g., information uncertainty, anxiety, and indecision, as seen in the Prisoner's Dilemma).

  12. Realistic tool-tissue interaction models for surgical simulation and planning

    NARCIS (Netherlands)

    Misra, Sarthak

    2009-01-01

    Surgical simulators present a safe and potentially effective method for surgical training, and can also be used in pre- and intra-operative surgical planning. Realistic modeling of medical interventions involving tool-tissue interactions has been considered to be a key requirement in the development

  13. Numerical modeling of Po-218 deposition in a physiologically realistic lung bifurcation model

    Science.gov (United States)

    Mously-Soroujy, Khalid Ahmad

    Experimental data for lung bifurcations reveals complex geometries and distinct asymmetrical characteristic, which affects the localized distribution of particles deposited in the lung. This study is based on recently published numerical results for a symmetric physiological realistic bifurcation geometry Heistracher and Hofmann (1995) which has been extended here to the case of a asymmetric geometry. The asymmetric PRB model was used to study the flow field and the deposition of ultrafine particles for inspiratory and expiratory conditions. In the present study, we investigated the effect of different flow rates, representing human activity and deposition of different ultrafine particles representing radon daughter (Po-218), in the PRB model. Numerical results were compared with the limited available experimental and numerical data. The fluid dynamic computer program FIDAP was used for this purpose.

  14. Realistic three-generation models from SO(32) heterotic string theory

    CERN Document Server

    Abe, Hiroyuki; Otsuka, Hajime; Takano, Yasufumi

    2015-01-01

    We search for realistic supersymmetric standard-like models from SO(32) heterotic string theory on factorizable tori with multiple magnetic fluxes. Three chiral ganerations of quarks and leptons are derived from the adjoint and vector representations of SO(12) gauge groups embedded in SO(32) adjoint representation. Massless spectra of our models also include Higgs fields, which have desired Yukawa couplings to quarks and leptons at the tree-level.

  15. Multidimensional realistic modelling of Cepheid-like variables-II: Analysis of a Cepheid model

    CERN Document Server

    Mundprecht, Eva; Kupka, Friedrich

    2015-01-01

    Non-local, time-dependent convection models have been used in the literature to explain the location of double-mode pulsations in Cepheids in the HR diagram as well as the existence and location of the red edge of the Cepheid instability strip. These properties are highly sensitive to model parameters. We use 2D radiation hydrodynamical simulations with realistic microphysics and grey radiative-transfer to model the upper 42 % of a short period Cepheid. The simulations show that the strength of the convection zone varies significantly over the pulsation period and exhibits a phase shift of the convective flux relative to the variations in radius. We evaluate the convective flux and the work performed by volume expansion as predicted by the most commonly used convection models. It turns out that over one pulsation cycle the model parameter $\\alpha_{\\rm c}$, which is proportional to the convective flux, has to be varied by up to a factor of beyond 2 to match the convective flux obtained from the simulations. To...

  16. Realistic and Spherical Head Modeling for EEG Forward Problem Solution: A Comparative Cortex-Based Analysis

    Science.gov (United States)

    Vatta, Federica; Meneghini, Fabio; Esposito, Fabrizio; Mininel, Stefano; Di Salle, Francesco

    2010-01-01

    The accuracy of forward models for electroencephalography (EEG) partly depends on head tissues geometry and strongly affects the reliability of the source reconstruction process, but it is not yet clear which brain regions are more sensitive to the choice of different model geometry. In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data. Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model. Point Spread Function (PSF) and Lead Field (LF) cross-correlation analyses were performed for 26 symmetric dipole sources to quantitatively assess models' accuracy in EEG source reconstruction. Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex. PMID:20169107

  17. Modeling of ultrasonic wave propagation in composite laminates with realistic discontinuity representation.

    Science.gov (United States)

    Zelenyak, Andreea-Manuela; Schorer, Nora; Sause, Markus G R

    2017-06-20

    This paper presents a method for embedding realistic defect geometries of a fiber reinforced material in a finite element modeling environment in order to simulate active ultrasonic inspection. When ultrasonic inspection is used experimentally to investigate the presence of defects in composite materials, the microscopic defect geometry may cause signal characteristics that are difficult to interpret. Hence, modeling of this interaction is key to improve our understanding and way of interpreting the acquired ultrasonic signals. To model the true interaction of the ultrasonic wave field with such defect structures as pores, cracks or delamination, a realistic three dimensional geometry reconstruction is required. We present a 3D-image based reconstruction process which converts computed tomography data in adequate surface representations ready to be embedded for processing with finite element methods. Subsequent modeling using these geometries uses a multi-scale and multi-physics simulation approach which results in quantitative A-Scan ultrasonic signals which can be directly compared with experimental signals. Therefore, besides the properties of the composite material, a full transducer implementation, piezoelectric conversion and simultaneous modeling of the attached circuit is applied. Comparison between simulated and experimental signals provides very good agreement in electrical voltage amplitude and the signal arrival time and thus validates the proposed modeling approach. Simulating ultrasound wave propagation in a medium with a realistic shape of the geometry clearly shows a difference in how the disturbance of the waves takes place and finally allows more realistic modeling of A-scans. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Engine inlet distortion in a 9.2 percent scale vectored thrust STOVL model in ground effect

    Science.gov (United States)

    Johns, Albert L.; Neiner, George; Flood, J. D.; Amuedo, K. C.; Strock, T. W.

    1989-01-01

    Advanced Short Takeoff/Vertical Landing (STOVL) aircraft which can operate from remote locations, damaged runways, and small air capable ships are being pursued for deployment around the turn of the century. To achieve this goal, NASA Lewis Research Center, McDonnell Douglas Aircraft, and DARPA defined a cooperative program for testing in the NASA Lewis 9- by 15-foot low speed wind tunnel (LSWT) to establish a database for hot gas ingestion, one of the technologies critical to STOVL. Results are presented which show the engine inlet distortions (both temperature and pressure) in a 9.2 percent scale vectored thrust STOVL model in ground effects. Results are shown for the forward nozzle splay angles of 0 degrees, -6 degrees, and 18 degrees. The model support system had 4 degrees of freedom, heated high pressure air for nozzle flow, and a suction system exhaust for inlet flow. The headwind (freestream) velocity was varied from 8 to 23 knots.

  19. Engine inlet distortion in a 9.2 percent scaled vectored thrust STOVL model in ground effect

    Science.gov (United States)

    Johns, Albert L.; Neiner, George; Flood, J. D.; Amuedo, K. C.; Strock, T. W.

    1989-01-01

    Advanced Short Takeoff/Vertical Landing (STOVL) aircraft which can operate from remote locations, damaged runways, and small air capable ships are being pursued for deployment around the turn of the century. To achieve this goal, a cooperative program has been defined for testing in the NASA Lewis 9- by 15-foot Low Speed Wind Tunnel (LSWT) to establish a database for hot gas ingestion, one of the technologies critical to STOVL. This paper presents results showing the engine inlet distortions (both temperature and pressure) in a 9.2 percent scale Vectored Thrust STOVL model in ground effects. Results are shown for the forward nozzle splay angles of 0, -6, and 18 deg. The model support system had 4 deg of freedom, heated high pressure air for nozzle flow, and a suction system exhaust for inlet flow. The headwind (freestream) velocity was varied from 8 to 23 kn.

  20. Numerical Modeling of Plasmonic Nanoantennas with Realistic 3D Roughness and Distortion

    Directory of Open Access Journals (Sweden)

    Vladimir P. Drachev

    2011-07-01

    Full Text Available Nanostructured plasmonic metamaterials, including optical nanoantenna arrays, are important for advanced optical sensing and imaging applications including surface-enhanced fluorescence, chemiluminescence, and Raman scattering. Although designs typically use ideally smooth geometries, realistic nanoantennas have nonzero roughness, which typically results in a modified enhancement factor that should be involved in their design. Herein we aim to treat roughness by introducing a realistic roughened geometry into the finite element (FE model. Even if the roughness does not result in significant loss, it does result in a spectral shift and inhomogeneous broadening of the resonance, which could be critical when fitting the FE simulations of plasmonic nanoantennas to experiments. Moreover, the proposed approach could be applied to any model, whether mechanical, acoustic, electromagnetic, thermal, etc, in order to simulate a given roughness-generated physical phenomenon.

  1. Fault-Tolerant Robot Programming through Simulation with Realistic Sensor Models

    OpenAIRE

    Axel Waggershauser; Thomas Braeunl; Andreas Koestler

    2008-01-01

    We introduce a simulation system for mobile robots that allows a realistic interaction of multiple robots in a common environment. The simulated robots are closely modeled after robots from the EyeBot family and have an identical application programmer interface. The simulation supports driving commands at two levels of abstraction as well as numerous sensors such as shaft encoders, infrared distance sensors, and compass. Simulation of on-board digital cameras via synthetic images allows the ...

  2. Residual water transport in the Marsdiep tidal inlet inferred from observations and a numerical model

    NARCIS (Netherlands)

    Sassi, M.G.; Gerkema, T.; Duran-Matute, M.; Nauw, J.J.

    2016-01-01

    At tidal inlets, large amounts of water are exchanged with the adjacent sea during the tidal cycle.The residual flows, the net effect of ebb and flood, are generally small compared with the gross flux;they vary in magnitude and sign from one tidal period to the other; and their long-term mean

  3. Towards a unified realistic shell-model Hamiltonian with the monopole-based universal force

    CERN Document Server

    Kaneko, K; Sun, Y; Tazaki, S

    2013-01-01

    We propose a unified realistic shell-model Hamiltonian employing the pairing plus multipole Hamiltonian combined with the monopole interaction constructed starting from the monopole-based universal force by Otsuka it et al. (Phys. Rev. Lett. 104, 012501 (2010)). It is demonstrated that the proposed PMMU model can consistently describe a large amount of spectroscopic data as well as binding energies in the pf and pf5/2g9/2 shell spaces, and could serve as a practical shell model for even heavier mass regions.

  4. Simplified realistic human head model for simulating Tumor Treating Fields (TTFields).

    Science.gov (United States)

    Wenger, Cornelia; Bomzon, Ze'ev; Salvador, Ricardo; Basser, Peter J; Miranda, Pedro C

    2016-08-01

    Tumor Treating Fields (TTFields) are alternating electric fields in the intermediate frequency range (100-300 kHz) of low-intensity (1-3 V/cm). TTFields are an anti-mitotic treatment against solid tumors, which are approved for Glioblastoma Multiforme (GBM) patients. These electric fields are induced non-invasively by transducer arrays placed directly on the patient's scalp. Cell culture experiments showed that treatment efficacy is dependent on the induced field intensity. In clinical practice, a software called NovoTalTM uses head measurements to estimate the optimal array placement to maximize the electric field delivery to the tumor. Computational studies predict an increase in the tumor's electric field strength when adapting transducer arrays to its location. Ideally, a personalized head model could be created for each patient, to calculate the electric field distribution for the specific situation. Thus, the optimal transducer layout could be inferred from field calculation rather than distance measurements. Nonetheless, creating realistic head models of patients is time-consuming and often needs user interaction, because automated image segmentation is prone to failure. This study presents a first approach to creating simplified head models consisting of convex hulls of the tissue layers. The model is able to account for anisotropic conductivity in the cortical tissues by using a tensor representation estimated from Diffusion Tensor Imaging. The induced electric field distribution is compared in the simplified and realistic head models. The average field intensities in the brain and tumor are generally slightly higher in the realistic head model, with a maximal ratio of 114% for a simplified model with reasonable layer thicknesses. Thus, the present pipeline is a fast and efficient means towards personalized head models with less complexity involved in characterizing tissue interfaces, while enabling accurate predictions of electric field distribution.

  5. General description of KAERI LBLOCA realistic evaluation model (REM) for ECCS evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Yong; Lee, Young Jin; Chung, Bub Dong; Lee, Won Jae [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1994-06-01

    A realistic evaluation model (REM) for LBLOCA licensing calculation is developed for application to pressurezed ligh water reactors. The developmental aim of the KAERI-REM is to provide a systematic methodology that is simple in structure and to used and built upon sound logical reasoning, for improving the code capability to realistically describe the LBLOCA phenomena and for evaluating the associated uncertainties. The method strives to be faithful to the intention of being best-estimate, that is, the method aims to evaluate the best-estimate values and the associated uncertainties while complying to the requirements in the ECCS regulations. As a demonstration, KAERI-REM was applied to quantify the safety margin for LBLOCA for Kori 3 and 4 and appended to this report. (Author) 11 refs., 2 figs., 6 tabs.

  6. The effect of a realistic thermal diffusivity on numerical model of a subducting slab

    Science.gov (United States)

    Maierova, P.; Steinle-Neumann, G.; Cadek, O.

    2010-12-01

    A number of numerical studies of subducting slab assume simplified (constant or only depth-dependent) models of thermal conductivity. The available mineral physics data indicate, however, that thermal diffusivity is strongly temperature- and pressure-dependent and may also vary among different mantle materials. In the present study, we examine the influence of realistic thermal properties of mantle materials on the thermal state of the upper mantle and the dynamics of subducting slabs. On the basis of the data published in mineral physics literature we compile analytical relationships that approximate the pressure and temperature dependence of thermal diffusivity for major mineral phases of the mantle (olivine, wadsleyite, ringwoodite, garnet, clinopyroxenes, stishovite and perovskite). We propose a simplified composition of mineral assemblages predominating in the subducting slab and the surrounding mantle (pyrolite, mid-ocean ridge basalt, harzburgite) and we estimate their thermal diffusivity using the Hashin-Shtrikman bounds. The resulting complex formula for the diffusivity of each aggregate is then approximated by a simpler analytical relationship that is used in our numerical model as an input parameter. For the numerical modeling we use the Elmer software (open source finite element software for multiphysical problems, see http://www.csc.fi/english/pages/elmer). We set up a 2D Cartesian thermo-mechanical steady-state model of a subducting slab. The model is partly kinematic as the flow is driven by a boundary condition on velocity that is prescribed on the top of the subducting lithospheric plate. Reology of the material is non-linear and is coupled with the thermal equation. Using the realistic relationship for thermal diffusivity of mantle materials, we compute the thermal and flow fields for different input velocity and age of the subducting plate and we compare the results against the models assuming a constant thermal diffusivity. The importance of the

  7. What is the most realistic single-compartment model of spike initiation?

    Directory of Open Access Journals (Sweden)

    Romain Brette

    2015-04-01

    Full Text Available A large variety of neuron models are used in theoretical and computational neuroscience, and among these, single-compartment models are a popular kind. These models do not explicitly include the dendrites or the axon, and range from the Hodgkin-Huxley (HH model to various flavors of integrate-and-fire (IF models. The main classes of models differ in the way spikes are initiated. Which one is the most realistic? Starting with some general epistemological considerations, I show that the notion of realism comes in two dimensions: empirical content (the sort of predictions that a model can produce and empirical accuracy (whether these predictions are correct. I then examine the realism of the main classes of single-compartment models along these two dimensions, in light of recent experimental evidence.

  8. Uncertainty Quantification of Tracer Dispersion with the PMVP Model under Realistic Conditions

    Science.gov (United States)

    Meyer, D. W.; Duenser, S.

    2015-12-01

    The polar Markovian velocity process (PVMP) model provides a computationally efficient method to propagate input uncertainty stemming from unknown permeability fields to output flow and transport statistics [Meyer and Tchelepi, WRR, 2010; Meyer, Jenny, and Tchelepi, WRR, 2010; Meyer et al., WRR, 2013]. Compared with classical Monte Carlo (MC) sampling, the PMVP model provides predictions of tracer concentration statistics at computing times that are three orders of magnitude smaller. Consequently, the PMVP model is as well significantly faster than accelerated sampling techniques such as multi-level MC or polynomial chaos expansions. In this work, we further evaluate the PMVP model performance by applying the model for tracer dispersion predictions in a setup derived from the well-known MADE field experiment [Boggs et al., WRR, 1992]. We perform detailed model validations against reference MC simulations and conclude that the model provides overall accurate dispersion predictions under realistic conditions.

  9. Model-based Evaluation of Location-based Relaying Policies in a Realistic Mobile Indoor Scenario

    DEFF Research Database (Denmark)

    Nielsen, Jimmy Jessen; Olsen, Rasmus Løvenstein; Madsen, Tatiana Kozlova

    2012-01-01

    developed Markov Chain model for a realistic indoor scenario that is based on ray-tracing enriched measurements from the WHERE2 project. These results are furthermore compared to results obtained using an idealistic path loss model, and it is shown that the performance impact of node mobility......For WLAN systems in which relaying is exploited for improving throughput performance, node mobility and in- formation collection delays can have a significant impact on the performance of a relay selection scheme. This paper analyzes this influence on the decision process using a previously...... and information collection delays is significantly different for the two data sets....

  10. Towards a realistic interpretation of quantum physics providing a physical model of the natural world

    CERN Document Server

    Santos, Emilio

    2012-01-01

    It is stressed the advantage of a realistic interpretation of quantum mechanics providing a physical model of the quantum world. After some critical comments on the most popular interpretations, the difficulties for a model are pointed out and possible solutions proposed. In particular the existence of discrete states, the quantum jumps, the alleged lack of objective properties, measurement theory, the probabilistic character of quantum physics, the wave-particle duality and the Bell inequalities are commented. It is conjectured that an intuitive picture of the quantum world could be obtained compatible with the quantum predictions for actual experiments, although maybe incompatible with alleged predictions for ideal, unrealizable, experiments.

  11. Multiscale modeling of polycrystalline graphene: A comparison of structure and defect energies of realistic samples from phase field crystal models

    Science.gov (United States)

    Hirvonen, Petri; Ervasti, Mikko M.; Fan, Zheyong; Jalalvand, Morteza; Seymour, Matthew; Vaez Allaei, S. Mehdi; Provatas, Nikolas; Harju, Ari; Elder, Ken R.; Ala-Nissila, Tapio

    2016-07-01

    We extend the phase field crystal (PFC) framework to quantitative modeling of polycrystalline graphene. PFC modeling is a powerful multiscale method for finding the ground state configurations of large realistic samples that can be further used to study their mechanical, thermal, or electronic properties. By fitting to quantum-mechanical density functional theory (DFT) calculations, we show that the PFC approach is able to predict realistic formation energies and defect structures of grain boundaries. We provide an in-depth comparison of the formation energies between PFC, DFT, and molecular dynamics (MD) calculations. The DFT and MD calculations are initialized using atomic configurations extracted from PFC ground states. Finally, we use the PFC approach to explicitly construct large realistic polycrystalline samples and characterize their properties using MD relaxation to demonstrate their quality.

  12. Introducing a more realistic model for opinion formation considering instability in social structure

    Science.gov (United States)

    Salehi, Sajjad; Taghiyareh, Fattaneh

    2016-06-01

    Opinion formation is a process through which interactions of individuals and dynamism of their opinions in effect of neighbors are modeled. In this paper, in an effort to model the opinion formation more realistically, we have introduced a model that considers the role of network structure in opinion dynamics. In this model, each individual changes his opinion in a way so as to decrease its difference with the opinion of trusted neighbors while he intensifies his dissention with the untrusted ones. Considering trust/distrust relations as a signed network, we have defined a structural indicator which shows the degree of instability in social structure and is calculated based on the structural balance theory. It is also applied as feedback to the opinion formation process affecting its dynamics. Our simulation results show formation of a set of clusters containing individuals holding opinions having similar values. Also, the opinion value of each individual is far from the ones of distrusted neighbors. Since this model considers distrust and instability of relations in society, it can offer a more realistic model of opinion formation.

  13. Analytical Model of Inlet Growth and Equilibrium Cross-Sectional Area

    Science.gov (United States)

    2016-04-01

    Sectional Area by Richard Styles PURPOSE: This Coastal and Hydraulics Engineering Technical Note (CHETN) focuses on inlet stability theory in...earlier treatments, Escoffier used the hydraulic radius instead of water depth in the friction term (Walton and Escoffier 1981). However, the ratio of...a0) tidal amplitude ratio. The details can be found in his original work and are not presented here except to note that Escoffier introduced two

  14. The ultimate signal-to-noise ratio in realistic body models.

    Science.gov (United States)

    Guérin, Bastien; Villena, Jorge F; Polimeridis, Athanasios G; Adalsteinsson, Elfar; Daniel, Luca; White, Jacob K; Wald, Lawrence L

    2016-12-04

    We compute the ultimate signal-to-noise ratio (uSNR) and G-factor (uGF) in a realistic head model from 0.5 to 21 Tesla. We excite the head model and a uniform sphere with a large number of electric and magnetic dipoles placed at 3 cm from the object. The resulting electromagnetic fields are computed using an ultrafast volume integral solver, which are used as basis functions for the uSNR and uGF computations. Our generalized uSNR calculation shows good convergence in the sphere and the head and is in close agreement with the dyadic Green's function approach in the uniform sphere. In both models, the uSNR versus B0 trend was linear at shallow depths and supralinear at deeper locations. At equivalent positions, the rate of increase of the uSNR with B0 was greater in the sphere than in the head model. The uGFs were lower in the realistic head than in the sphere for acceleration in the anterior-posterior direction, but similar for the left-right direction. The uSNR and uGFs are computable in nonuniform body models and provide fundamental performance limits for human imaging with close-fitting MRI array coils. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  15. Time-variability of alpha from realistic models of Oklo reactors

    Science.gov (United States)

    Gould, Chris; Sharapov, Eduard; Lamoreaux, Steve

    2006-10-01

    We reanalyze Oklo ^149Sm data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of α, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the ^149Sm effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient ^149Sm effective cross sections, and use these values to set limits on the time-variation of α. Our study resolves a contradictory situation with previous Oklo α-results. Our suggested 2 σ bound on a possible time variation of α over two billion years is stringent: -0.11 <=δαα <=0.24, in units of 10-7, but model dependent in that it assumes only α has varied over time.

  16. Developing a realistic model for the training of the laparoscopic Nissen fundoplication.

    Science.gov (United States)

    Botden, Sanne M B I; Goossens, Richard; Jakimowicz, Jack J

    2010-06-01

    A realistic human anatomy simulation model developed for training to perform laparoscopic Nissen fundoplication (antireflux surgery) could reduce the need and use of animal tissue models. This article elaborates the designing process of this model and the development process used to create the abdominal organs with realistic haptic feedback. Before developing the artificial organs, first the mechanical characteristics of human tissue were examined. Next, separate animal organs that resembled these characteristics the closest was used to create the model. The haptic feedback of the intra-abdominal organs variables studied included tissue, geometry, and context. The stress-strain curves of the different tissues were calculated and compared with the properties of industrial materials to find the best material for the production of the organs. The aspects that influenced haptic feedback as determined above and used to select the most promising material groups were: E-modulus, density, coefficient of friction, sensitivity to tearing, wall thickness, and shelf life. Based on these criteria, silicone and latex materials mimiked human tissue best. Changeable velvet rope was used for connections of the organs to the surface and other simulated tissue. A reusable modular model of the upper abdomen anatomy with haptic properties was created for training of upper gastrointestinal surgery laparoscopic procedures, such as the Nissen fundoplication.

  17. Modelling realistic horizontal branch morphologies and their impact on spectroscopic ages of unresolved stellar systems

    CERN Document Server

    Percival, Susan M

    2010-01-01

    The presence of an extended blue horizontal branch (HB) in a stellar population is known to affect the age inferred from spectral fitting to stellar population synthesis models. However, most population synthesis models still rely on theoretical isochrones which do not include realistic modelling of extended HBs. In this work, we create detailed models for a range of old simple stellar populations (SSPs), to create a variety of realistic HB morphologies, from extended red clumps, to extreme blue HBs. We achieve this by utilising stellar tracks from the BaSTI database and implementing a different mass loss prescription for each SSP created, resulting in different HB morphologies. We find that, for each metallicity, there is some HB morphology which maximises Hbeta, making an underlying 14Gyr population look ~5-6Gyr old for the low and intermediate metallicity cases, and as young as 2Gyr for a solar metallicity SSP. We explore whether there are any spectral indices capable of breaking the degeneracy between an ...

  18. Increasing pulse wave velocity in a realistic cardiovascular model does not increase pulse pressure with age

    Science.gov (United States)

    Mohiuddin, Mohammad W.; Rihani, Ryan J.; Laine, Glen A.

    2012-01-01

    The mechanism of the well-documented increase in aortic pulse pressure (PP) with age is disputed. Investigators assuming a classical windkessel model believe that increases in PP arise from decreases in total arterial compliance (Ctot) and increases in total peripheral resistance (Rtot) with age. Investigators assuming a more sophisticated pulse transmission model believe PP rises because increases in pulse wave velocity (cph) make the reflected pressure wave arrive earlier, augmenting systolic pressure. It has recently been shown, however, that increases in cph do not have a commensurate effect on the timing of the reflected wave. We therefore used a validated, large-scale, human arterial system model that includes realistic pulse wave transmission to determine whether increases in cph cause increased PP with age. First, we made the realistic arterial system model age dependent by altering cardiac output (CO), Rtot, Ctot, and cph to mimic the reported changes in these parameters from age 30 to 70. Then, cph was theoretically maintained constant, while Ctot, Rtot, and CO were altered. The predicted increase in PP with age was similar to the observed increase in PP. In a complementary approach, Ctot, Rtot, and CO were theoretically maintained constant, and cph was increased. The predicted increase in PP was negligible. We found that increases in cph have a limited effect on the timing of the reflected wave but cause the system to degenerate into a windkessel. Changes in PP can therefore be attributed to a decrease in Ctot. PMID:22561301

  19. Realistic multi-cellular dosimetry for (177)Lu-labelled antibodies: model and application.

    Science.gov (United States)

    Marcatili, S; Pichard, A; Courteau, A; Ladjohounlou, R; Navarro-Teulon, I; Repetto-Llamazares, A; Heyerdahl, H; Dahle, J; Pouget, J P; Bardiès, M

    2016-10-07

    Current preclinical dosimetric models often fail to take account of the complex nature of absorbed dose distribution typical of in vitro clonogenic experiments in targeted radionuclide therapy. For this reason, clonogenic survival is often expressed as a function of added activity rather than the absorbed dose delivered to cells/cell nuclei. We designed a multi-cellular dosimetry model that takes into account the realistic distributions of cells in the Petri dish, for the establishment of survival curves as a function of the absorbed dose. General-purpose software tools were used for the generation of realistic, randomised 3D cell culture geometries based on experimentally determined parameters (cell size, cell density, cluster density, average cluster size, cell cumulated activity). A mixture of Monte Carlo and analytical approaches was implemented in order to achieve as accurate as possible results while reducing calculation time. The model was here applied to clonogenic survival experiments carried out to compare the efficacy of Betalutin(®), a novel (177)Lu-labelled antibody radionuclide conjugate for the treatment of non-Hodgkin lymphoma, to that of (177)Lu-labelled CD20-specific (rituximab) and non-specific antibodies (Erbitux) on lymphocyte B cells. The 3D cellular model developed allowed a better understanding of the radiative and non-radiative processes associated with cellular death. Our approach is generic and can also be applied to other radiopharmaceuticals and cell distributions.

  20. Realistic multi-cellular dosimetry for 177Lu-labelled antibodies: model and application

    Science.gov (United States)

    Marcatili, S.; Pichard, A.; Courteau, A.; Ladjohounlou, R.; Navarro-Teulon, I.; Repetto-Llamazares, A.; Heyerdahl, H.; Dahle, J.; Pouget, J. P.; Bardiès, M.

    2016-10-01

    Current preclinical dosimetric models often fail to take account of the complex nature of absorbed dose distribution typical of in vitro clonogenic experiments in targeted radionuclide therapy. For this reason, clonogenic survival is often expressed as a function of added activity rather than the absorbed dose delivered to cells/cell nuclei. We designed a multi-cellular dosimetry model that takes into account the realistic distributions of cells in the Petri dish, for the establishment of survival curves as a function of the absorbed dose. General-purpose software tools were used for the generation of realistic, randomised 3D cell culture geometries based on experimentally determined parameters (cell size, cell density, cluster density, average cluster size, cell cumulated activity). A mixture of Monte Carlo and analytical approaches was implemented in order to achieve as accurate as possible results while reducing calculation time. The model was here applied to clonogenic survival experiments carried out to compare the efficacy of Betalutin®, a novel 177Lu-labelled antibody radionuclide conjugate for the treatment of non-Hodgkin lymphoma, to that of 177Lu-labelled CD20-specific (rituximab) and non-specific antibodies (Erbitux) on lymphocyte B cells. The 3D cellular model developed allowed a better understanding of the radiative and non-radiative processes associated with cellular death. Our approach is generic and can also be applied to other radiopharmaceuticals and cell distributions.

  1. Time-variability of alpha from realistic models of Oklo reactors

    CERN Document Server

    Gould, C R; Lamoreaux, S K

    2006-01-01

    We reanalyze Oklo $^{149}$Sm data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of $\\alpha$, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the $^{149}$Sm effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient $^{149}$Sm effective cross sections, and use these values to set limits on the time-variation of $\\alpha$. Our study resolves a contradictory situation with previous Oklo $\\alpha$-results. Our suggested $2 \\sigma$ bound on a possible time variation of $\\alpha$ over two billion years is stringent: $ -...

  2. Development of a realistic in vivo bone metastasis model of human renal cell carcinoma.

    Science.gov (United States)

    Valta, Maija P; Zhao, Hongjuan; Ingels, Alexandre; Thong, Alan E; Nolley, Rosalie; Saar, Matthias; Peehl, Donna M

    2014-06-01

    About one-third of patients with advanced renal cell carcinoma (RCC) have bone metastases. The incidence of RCC is increasing and bone metastatic RCC merits greater focus. Realistic preclinical bone metastasis models of RCC are lacking, hampering the development of effective therapies. We developed a realistic in vivo bone metastasis model of human RCC by implanting precision-cut tissue slices under the renal capsule of immunodeficient mice. The presence of disseminated cells in bone marrow of tissue slice graft (TSG)-bearing mice was screened by human-specific polymerase chain reaction and confirmed by immunohistology using human-specific antibody. Disseminated tumor cells in bone marrow of TSG-bearing mice derived from three of seven RCC patients were detected as early as 1 month after tissue implantation at a high frequency with close resemblance to parent tumors (e.g., CAIX expression and high vascularity). The metastatic patterns of TSGs correlated with disease progression in patients. In addition, TSGs retained capacity to metastasize to bone at high frequency after serial passaging and cryopreservation. Moreover, bone metastases in mice responded to Temsirolimus treatment. Intratibial injections of single cells generated from TSGs showed 100 % engraftment and produced X-ray-visible tumors as early as 3 weeks after cancer cell inoculation. Micro-computed tomography (μCT) and histological analysis revealed osteolytic characteristics of these lesions. Our results demonstrated that orthotopic RCC TSGs have potential to develop bone metastases that respond to standard therapy. This first reported primary RCC bone metastasis model provides a realistic setting to test therapeutics to prevent or treat bone metastases in RCC.

  3. Leptogenesis in the Light of Super-Kamiokande Data and a Realistic String Model

    CERN Document Server

    Ellis, Jonathan Richard; Nanopoulos, Dimitri V; Ellis, John

    1999-01-01

    We discuss leptogenesis in the light of indications of neutrino masses and mixings from Super-Kamiokande and other data on atmospheric neutrinos, as well as the solar neutrino deficit. Neutrino masses and mixings consistent with these data may produce in a natural and generic way a lepton asymmetry that is suffient to provide the observed baryon asymmetry, after processing via non-perturbative electroweak effects. We illustrate this discussion in the framework of the string-derived flipped SU(5) model, using particle assignments and choices of vacuum parameters that are known to give realistic masses to quarks and charged leptons. We display one scenario for neutrino masses that also accommodates leptogenesis.

  4. Geometrical order-of-magnitude estimates for spatial curvature in realistic models of the Universe

    CERN Document Server

    Buchert, Thomas; van Elst, Henk; 10.1007/s10714-009-0828-4

    2009-01-01

    The thoughts expressed in this article are based on remarks made by J\\"urgen Ehlers at the Albert-Einstein-Institut, Golm, Germany in July 2007. The main objective of this article is to demonstrate, in terms of plausible order-of-magnitude estimates for geometrical scalars, the relevance of spatial curvature in realistic models of the Universe that describe the dynamics of structure formation since the epoch of matter-radiation decoupling. We introduce these estimates with a commentary on the use of a quasi-Newtonian metric form in this context.

  5. Semantic modeling for theory clarification: The realist vs liberal international relations perspective

    Energy Technology Data Exchange (ETDEWEB)

    Bray, O.H. [Sandia National Labs., Albuquerque, NM (United States)]|[Univ. of New Mexico, Albuquerque, NM (United States). Political Science Dept.

    1994-04-01

    This paper describes a natural language based, semantic information modeling methodology and explores its use and value in clarifying and comparing political science theories and frameworks. As an example, the paper uses this methodology to clarify and compare some of the basic concepts and relationships in the realist (e.g. Waltz) and the liberal (e.g. Rosenau) paradigms for international relations. The methodology can provide three types of benefits: (1) it can clarify and make explicit exactly what is meant by a concept; (2) it can often identify unanticipated implications and consequence of concepts and relationships; and (3) it can help in identifying and operationalizing testable hypotheses.

  6. Plasticity-modulated seizure dynamics for seizure termination in realistic neuronal models

    Science.gov (United States)

    Koppert, M. M. J.; Kalitzin, S.; Lopes da Silva, F. H.; Viergever, M. A.

    2011-08-01

    In previous studies we showed that autonomous absence seizure generation and termination can be explained by realistic neuronal models eliciting bi-stable dynamics. In these models epileptic seizures are triggered either by external stimuli (reflex epilepsies) or by internal fluctuations. This scenario predicts exponential distributions of the duration of the seizures and of the inter-ictal intervals. These predictions were validated in rat models of absence epilepsy, as well as in a few human cases. Nonetheless, deviations from the predictions with respect to seizure duration distributions remained unexplained. The objective of the present work is to implement a simple but realistic computational model of a neuronal network including synaptic plasticity and ionic current dynamics and to explore the dynamics of the model with special emphasis on the distributions of seizure and inter-ictal period durations. We use as a basis our lumped model of cortical neuronal circuits. Here we introduce 'activity dependent' parameters, namely post-synaptic voltage-dependent plasticity, as well as a voltage-dependent hyperpolarization-activated current driven by slow and fast activation conductances. We examine the distributions of the durations of the seizure-like model activity and the normal activity, described respectively by the limit cycle and the steady state in the dynamics. We use a parametric γ-distribution fit as a quantifier. Our results show that autonomous, activity-dependent membrane processes can account for experimentally obtained statistical distributions of seizure durations, which were not explainable using the previous model. The activity-dependent membrane processes that display the strongest effect in accounting for these distributions are the hyperpolarization-dependent cationic (Ih) current and the GABAa plastic dynamics. Plastic synapses (NMDA-type) in the interneuron population show only a minor effect. The inter-ictal statistics retain their

  7. Fast Realistic MRI Simulations Based on Generalized Multi-Pool Exchange Tissue Model.

    Science.gov (United States)

    Liu, Fang; Velikina, Julia V; Block, Walter F; Kijowski, Richard; Samsonov, Alexey A

    2017-02-01

    We present MRiLab, a new comprehensive simulator for large-scale realistic MRI simulations on a regular PC equipped with a modern graphical processing unit (GPU). MRiLab combines realistic tissue modeling with numerical virtualization of an MRI system and scanning experiment to enable assessment of a broad range of MRI approaches including advanced quantitative MRI methods inferring microstructure on a sub-voxel level. A flexible representation of tissue microstructure is achieved in MRiLab by employing the generalized tissue model with multiple exchanging water and macromolecular proton pools rather than a system of independent proton isochromats typically used in previous simulators. The computational power needed for simulation of the biologically relevant tissue models in large 3D objects is gained using parallelized execution on GPU. Three simulated and one actual MRI experiments were performed to demonstrate the ability of the new simulator to accommodate a wide variety of voxel composition scenarios and demonstrate detrimental effects of simplified treatment of tissue micro-organization adapted in previous simulators. GPU execution allowed  ∼ 200× improvement in computational speed over standard CPU. As a cross-platform, open-source, extensible environment for customizing virtual MRI experiments, MRiLab streamlines the development of new MRI methods, especially those aiming to infer quantitatively tissue composition and microstructure.

  8. Modeling short-term dynamics and variability for realistic interactive facial animation.

    Science.gov (United States)

    Stoiber, Nicolas; Breton, Gaspard; Seguier, Renaud

    2010-01-01

    Modern modeling and rendering techniques have produced nearly photorealistic face models, but truly expressive digital faces also require natural-looking movements. Virtual characters in today's applications often display unrealistic facial expressions. Indeed, facial animation with traditional schemes such as keyframing and motion capture demands expertise. Moreover, the traditional schemes aren't adapted to interactive applications that require the real-time generation of context-dependent movements. A new animation system produces realistic expressive facial motion at interactive speed. The system relies on a set of motion models controlling facial-expression dynamics. The models are fitted on captured motion data and therefore retain the dynamic signature of human facial expressions. They also contain a nondeterministic component that ensures the variety of the long-term visual behavior. This system can efficiently animate any synthetic face. The video illustrates interactive use of a system that generates facial-animation sequences.

  9. Validation of a realistic, simple, and inexpensive EUS-FNA training model using isolated porcine stomach.

    Science.gov (United States)

    Hoshi, Koki; Irisawa, Atsushi; Shibukawa, Goro; Yamabe, Akane; Fujisawa, Mariko; Igarashi, Ryo; Yoshida, Yoshitsugu; Abe, Yoko; Imbe, Koh

    2016-09-01

    Trainees are required to learn EUS-FNA using a model before working with a patient. The aim of the current study was to validate a new training model developed for EUS-FNA. Several fresh chicken tenderloins were embedded as target lesions in the submucosal layer of an isolated porcine stomach. The stomach was fixed to a plate with nails, and was placed in a tub filled with water. The primary endpoint was feasibility of the newly developed model for EUS-FNA training, evaluated as follows: 1) visualization of the target lesion with blinding for lesion location; 2) penetrability of the needle; 3) sampling rate of macroscopic specimen; and 4) ROSE capability. Secondary endpoints were its durability and utility for multiple EUS-FNA procedures during EUS-FNA training, and the ease and cost of preparing the model. Six endoscopists (1 expert, 5 trainees) attempted EUS-FNA procedures using this model. The target lesion could be identified clearly, and EUS-FNA could be performed with realistic resistance felt. In addition, rapid on-site evaluation could be easily achieved. Based on 10 needlings by each endoscopist, adequate specimens for histology could be macroscopically taken with an average 85 % success rate. Visibility and maneuverability were maintained throughout all needlings. Preparation time for this model was less than 30 minutes with a total cost of $ 22. An easy-to-use and inexpensive training model with a realistic feel of needling was created. This model can potentially enable beginners to practice safe and effective EUS-FNA procedures.

  10. Realistic Modeling of Multi-Scale MHD Dynamics of the Solar Atmosphere

    Science.gov (United States)

    Kitiashvili, Irina; Mansour, Nagi N.; Wray, Alan; Couvidat, Sebastian; Yoon, Seokkwan; Kosovichev, Alexander

    2014-01-01

    Realistic 3D radiative MHD simulations open new perspectives for understanding the turbulent dynamics of the solar surface, its coupling to the atmosphere, and the physical mechanisms of generation and transport of non-thermal energy. Traditionally, plasma eruptions and wave phenomena in the solar atmosphere are modeled by prescribing artificial driving mechanisms using magnetic or gas pressure forces that might arise from magnetic field emergence or reconnection instabilities. In contrast, our 'ab initio' simulations provide a realistic description of solar dynamics naturally driven by solar energy flow. By simulating the upper convection zone and the solar atmosphere, we can investigate in detail the physical processes of turbulent magnetoconvection, generation and amplification of magnetic fields, excitation of MHD waves, and plasma eruptions. We present recent simulation results of the multi-scale dynamics of quiet-Sun regions, and energetic effects in the atmosphere and compare with observations. For the comparisons we calculate synthetic spectro-polarimetric data to model observational data of SDO, Hinode, and New Solar Telescope.

  11. A Madden-Julian oscillation event realistically simulated by a global cloud-resolving model.

    Science.gov (United States)

    Miura, Hiroaki; Satoh, Masaki; Nasuno, Tomoe; Noda, Akira T; Oouchi, Kazuyoshi

    2007-12-14

    A Madden-Julian Oscillation (MJO) is a massive weather event consisting of deep convection coupled with atmospheric circulation, moving slowly eastward over the Indian and Pacific Oceans. Despite its enormous influence on many weather and climate systems worldwide, it has proven very difficult to simulate an MJO because of assumptions about cumulus clouds in global meteorological models. Using a model that allows direct coupling of the atmospheric circulation and clouds, we successfully simulated the slow eastward migration of an MJO event. Topography, the zonal sea surface temperature gradient, and interplay between eastward- and westward-propagating signals controlled the timing of the eastward transition of the convective center. Our results demonstrate the potential making of month-long MJO predictions when global cloud-resolving models with realistic initial conditions are used.

  12. A Fibrocontractive Mechanochemical Model of Dermal Wound Closure Incorporating Realistic Growth Factor Kinetics

    KAUST Repository

    Murphy, Kelly E.

    2012-01-13

    Fibroblasts and their activated phenotype, myofibroblasts, are the primary cell types involved in the contraction associated with dermal wound healing. Recent experimental evidence indicates that the transformation from fibroblasts to myofibroblasts involves two distinct processes: The cells are stimulated to change phenotype by the combined actions of transforming growth factor β (TGFβ) and mechanical tension. This observation indicates a need for a detailed exploration of the effect of the strong interactions between the mechanical changes and growth factors in dermal wound healing. We review the experimental findings in detail and develop a model of dermal wound healing that incorporates these phenomena. Our model includes the interactions between TGFβ and collagenase, providing a more biologically realistic form for the growth factor kinetics than those included in previous mechanochemical descriptions. A comparison is made between the model predictions and experimental data on human dermal wound healing and all the essential features are well matched. © 2012 Society for Mathematical Biology.

  13. XCAT/DRASIM: a realistic CT/human-model simulation package

    Science.gov (United States)

    Fung, George S. K.; Stierstorfer, Karl; Segars, W. Paul; Taguchi, Katsuyuki; Flohr, Thomas G.; Tsui, Benjamin M. W.

    2011-03-01

    The aim of this research is to develop a complete CT/human-model simulation package by integrating the 4D eXtended CArdiac-Torso (XCAT) phantom, a computer generated NURBS surface based phantom that provides a realistic model of human anatomy and respiratory and cardiac motions, and the DRASIM (Siemens Healthcare) CT-data simulation program. Unlike other CT simulation tools which are based on simple mathematical primitives or voxelized phantoms, this new simulation package has the advantages of utilizing a realistic model of human anatomy and physiological motions without voxelization and with accurate modeling of the characteristics of clinical Siemens CT systems. First, we incorporated the 4D XCAT anatomy and motion models into DRASIM by implementing a new library which consists of functions to read-in the NURBS surfaces of anatomical objects and their overlapping order and material properties in the XCAT phantom. Second, we incorporated an efficient ray-tracing algorithm for line integral calculation in DRASIM by computing the intersection points of the rays cast from the x-ray source to the detector elements through the NURBS surfaces of the multiple XCAT anatomical objects along the ray paths. Third, we evaluated the integrated simulation package by performing a number of sample simulations of multiple x-ray projections from different views followed by image reconstruction. The initial simulation results were found to be promising by qualitative evaluation. In conclusion, we have developed a unique CT/human-model simulation package which has great potential as a tool in the design and optimization of CT scanners, and the development of scanning protocols and image reconstruction methods for improving CT image quality and reducing radiation dose.

  14. Satisfaction and sustainability: a realist review of decentralized models of perinatal surgery for rural women.

    Science.gov (United States)

    Kornelsen, Jude; McCartney, Kevin; Williams, Kim

    2016-01-01

    This article was developed as part of a larger realist review investigating the viability and efficacy of decentralized models of perinatal surgical services for rural women in the context of recent and ongoing service centralization witnessed in many developed nations. The larger realist review was commissioned by the British Columbia Ministry of Health and Perinatal Services of British Columbia, Canada. Findings from that review are addressed in this article specific to the sustainability of rural perinatal surgical sites and the satisfaction of providers that underpins their recruitment to and retention at such sites. A realist method was used in the selection and analysis of literature with the intention to iteratively develop a sophisticated understanding of how perinatal surgical services can best meet the needs of women who live in rural and remote environments. The goal of a realist review is to examine what works for whom under what circumstances and why. The high sensitivity search used language (English) and year (since 1990) limiters in keeping with both a realist and rapid review tradition of using reasoned contextual boundaries. No exclusions were made based on methodology or methodological approach in keeping with a realist review. Databases searched included MEDLINE, PubMed, EBSCO, CINAHL, EBM Reviews, NHS Economic Evaluation Database and PAIS International for literature in December 2013. Database searching produced 103 included academic articles. A further 59 resources were added through pearling and 13 grey literature reports were added on recommendation from the commissioner. A total of 42 of these 175 articles were included in this article as specific to provider satisfaction and service sustainability. Operative perinatal practice was found to be a lynchpin of sustainable primary and surgical services in rural communities. Rural shortages of providers, including challenges with recruitment and retention, were found to be a complex issue, with

  15. The boundary layer over turbine blade models with realistic rough surfaces

    Science.gov (United States)

    McIlroy, Hugh M., Jr.

    The impact of turbine blade surface roughness on aerodynamic performance and heat loads is well known. Over time, as the turbine blades are exposed to heat loads, the external surfaces of the blades become rough. Also, for film-cooled blades, surface degradation can have a significant impact on film-cooling effectiveness. Many studies have been conducted on the effects of surface degradation/roughness on engine performance but most investigations have modeled the rough surfaces with uniform or two-dimensional roughness patterns. The objective of the present investigation is to conduct measurements that will reveal the influence of realistic surface roughness on the near-wall behavior of the boundary layer. Measurements have been conducted at the Matched-Index-of-Refraction (MIR) Facility at the Idaho National Engineering and Environmental Laboratory with a laser Doppler velocimeter. A flat plate model of a turbine blade has been developed that produces a transitional boundary layer, elevated freestream turbulence and an accelerating freestream in order to simulate conditions on the suction side of a high-pressure turbine blade. Boundary layer measurements have been completed over a smooth plate model and over a model with a strip of realistic rough surface. The realistic rough surface was developed by scaling actual turbine blade surface data that was provided by U.S. Air Force Research Laboratory. The results indicate that bypass transition occurred very early in the flow over the model and that the boundary layer remained unstable throughout the entire length of the test plate; the boundary layer thickness and momentum thickness Reynolds numbers increased over the rough patch; and the shape factor increased over the rough patch but then decreased downstream of the patch relative to the smooth plate case; in the rough patch case the flow experienced two transition reversals with laminar-like behavior achieved by the end of the test plate; streamwise turbulence

  16. Coastal Inlets Research Program

    Science.gov (United States)

    2014-04-01

    2003 2005 2007 2009 2011 2013 Calendar Year CIRP Website: Tech Transfer http://cirp.usace.army.mil What new technology transfer do we have to discuss...etc.), nested grids; integrated with CMS-Flow Verification & Validation Cases (14) Bouss-2D: Phase -resolving shallow- water, nonlinear wave model for...Port Orford, OR Tillamook Inlet, OR  SPN: Half Moon Bay CA Waves at  Navigation  Structures ,  SWG: Matagorda Ship Channel, TX West Galveston

  17. Toward Affordable, Theory-and-Simulation-Inspired, Models for Realistic Wind Turbine Aerodynamics and Noise

    Science.gov (United States)

    Ladeinde, Foluso; Alabi, Ken; Li, Wenhai

    2015-11-01

    The problem of generating design data for the operation of a farm of wind turbines for clean energy production is quite complicated, if properly done. Potential flow theories provide some models, but these are not suitable for the massive aerodynamic separation and turbulence that characterize many realistic wind turbine applications. Procedures, such as computational fluid dynamics (CFD), which can potentially resolve some of the accuracy problems with the purely theoretical approach, are quite expensive to use, and often prohibit real-time design and control. In our work, we seek affordable and acceptably-accurate models derived from the foregoing approaches. The simulation used in our study is based on high-fidelity CFD, meaning that we use high-order (compact-scheme based), mostly large-eddy simulation methods, with due regards for the proper treatment of the stochastic inflow turbulence data. Progress on the project described herein will be presented.

  18. Quark-Lepton Mass Relation in a Realistic A4 Extension of the Standard Model

    CERN Document Server

    King, S F; Peinado, E; Valle, J W F

    2013-01-01

    We propose a realistic A4 extension of the Standard Model involving a particular quark-lepton mass relation, namely that the ratio of the third family mass to the geometric mean of the first and second family masses are equal for down-type quarks and charged leptons. This relation, which is approximately renormalization group invariant, is usually regarded as arising from the Georgi-Jarlskog relations, but in the present model there is no unification group or supersymmetry. In the neutrino sector we propose a simple modification of the so called Zee-Wolfenstein mass matrix pattern which allows an acceptable reactor angle along with a deviation of the atmospheric and solar angles from their bi-maximal values. Quark masses, mixing angles and CP violation are well described by a numerical fit.

  19. Fault-Tolerant Robot Programming through Simulation with Realistic Sensor Models

    Directory of Open Access Journals (Sweden)

    Axel Waggershauser

    2008-11-01

    Full Text Available We introduce a simulation system for mobile robots that allows a realistic interaction of multiple robots in a common environment. The simulated robots are closely modeled after robots from the EyeBot family and have an identical application programmer interface. The simulation supports driving commands at two levels of abstraction as well as numerous sensors such as shaft encoders, infrared distance sensors, and compass. Simulation of on-board digital cameras via synthetic images allows the use of image processing routines for robot control within the simulation. Specific error models for actuators, distance sensors, camera sensor, and wireless communication have been implemented. Progressively increasing error levels for an application program allows for testing and improving its robustness and fault-tolerance.

  20. Model of a realistic InP surface quantum dot extrapolated from atomic force microscopy results.

    Science.gov (United States)

    Barettin, Daniele; De Angelis, Roberta; Prosposito, Paolo; Auf der Maur, Matthias; Casalboni, Mauro; Pecchia, Alessandro

    2014-05-16

    We report on numerical simulations of a zincblende InP surface quantum dot (QD) on In₀.₄₈Ga₀.₅₂ buffer. Our model is strictly based on experimental structures, since we extrapolated a three-dimensional dot directly by atomic force microscopy results. Continuum electromechanical, [Formula: see text] bandstructure and optical calculations are presented for this realistic structure, together with benchmark calculations for a lens-shape QD with the same radius and height of the extrapolated dot. Interesting similarities and differences are shown by comparing the results obtained with the two different structures, leading to the conclusion that the use of a more realistic structure can provide significant improvements in the modeling of QDs fact, the remarkable splitting for the electron p-like levels of the extrapolated dot seems to prove that a realistic experimental structure can reproduce the right symmetry and a correct splitting usually given by atomistic calculations even within the multiband [Formula: see text] approach. Moreover, the energy levels and the symmetry of the holes are strongly dependent on the shape of the dot. In particular, as far as we know, their wave function symmetries do not seem to resemble to any results previously obtained with simulations of zincblende ideal structures, such as lenses or truncated pyramids. The magnitude of the oscillator strengths is also strongly dependent on the shape of the dot, showing a lower intensity for the extrapolated dot, especially for the transition between the electrons and holes ground state, as a result of a relevant reduction of the wave functions overlap. We also compare an experimental photoluminescence spectrum measured on an homogeneous sample containing about 60 dots with a numerical ensemble average derived from single dot calculations. The broader energy range of the numerical spectrum motivated us to perform further verifications, which have clarified some aspects of the experimental

  1. Photo-Realistic 3D Modelling of Sculptures on Open-Air Museums

    Directory of Open Access Journals (Sweden)

    Francesca Duca

    2011-12-01

    Full Text Available Laser scanning is a high-end technology with possibilities far ahead the well-known civil engineering and industrial applications. The actual geomatic technologies and methodologies for cultural heritage documentation allow the generation of very realistic 3D results used for many scopes like archaeological documentation, digital conservation, 3D repositories, etc. The fast acquisition times of large number of point clouds in 3D opens up the world of capabilities to document and keep alive cultural heritage, moving forward the generation of virtual animated replicas of great value and smooth multimedia dissemination. This paper presents the use of a terrestrial laser sca nning (TLS as a valuable tool for 3D documentation of large outdoor cultural heritage sculptures such as two of the existing ones inside the “Campus de Vera” of the UPV: “Defensas I” and “Mentoring”. The processing of the TLS data is discussed in detail in order to create photo-realistic digital models. Data acquisition is conducted with a time-of-flight scanner, characterized by its high accuracy, small beam, and ultra-fine scanning. Data processing is performed using Leica Geosystems Cyclone Software for the data registration and 3DReshaper Software for modelling and texturing.  High-resolution images after calibration and orientation of an off-the-shelf digital camera are draped onto the models to achieve right appearance in colour and texture. A discussion on the differences found out when modelling sculptures with different deviation errors will be presented. Processing steps such as normal smoothing and vertices recalculation are found appropriate to achieve continuous meshes around the objects.

  2. Realistic Modeling of Fast MHD Wave Trains in Coronal Active Regions

    Science.gov (United States)

    Ofman, Leon; Sun, Xudong

    2017-08-01

    Motivated by recent SDO/AIA observations we have developed realistic modeling of quasi-periodic, fast-mode propagating MHD wave trains (QFPs) using 3D MHD model initiated with potential magnetic field extrapolated from the solar coronal boundary. Localized quasi-periodic pulsations associated with C-class flares that drive the waves (as deduced from observations) are modeled with transverse periodic displacement of magnetic field at the lower coronal boundary. The modeled propagating speed and the form of the wave expansions matches the observed fast MHD waves speed >1000 km/s and topology. We study the parametric dependence of the amplitude, propagation, and damping of the waves for a range of key model parameters, such as the background temperature, density, and the location of the flaring site within the active region. We investigate the interaction of multiple QFP wave trains excited by adjacent flaring sources. We use the model results to synthesize EUV intensities in multiple AIA channels and obtain the model parameters that best reproduce the properties of observed QFPs, such as the recent DEM analysis. We discuss the implications of our modeling results for the seismological application of QFPs for the diagnostic of the active region field, flare pulsations, end estimate the energy flux carried by the waves.

  3. Predictive atomistic simulations of electronic properties of realistic nanoscale devices: A multiscale modeling approach

    Science.gov (United States)

    Vedula, Ravi Pramod Kumar

    profiles, inherent in strain-engineered Ge nanofins, on their transport properties. Fully atomistic simulations, involving a combination molecular dynamics simulations with first-principles based force-fields and semi-empirical tight binding calculations, coupled with linearized Boltzmann model are used to calculate the hole transport properties of realistic Ge nanofins (heights 5-15nm and widths 5nm-40nm). Our simulations predict the technological limit of phonon limited hole mobility improvement in Ge channel PMOS devices (Hengineer high performance uniaxial devices conducive to the existing top-down fabrication approaches. From these calculations, we demonstrate that realistic modeling of the devices requires a reduction in the empiricism of fitting parameters and incorporation of new multi-scale, multi-resolution approach spanning across various spatial and temporal scales. Such physics based predictive multiscale models facilitate an integrated approach for rapid development and pave the way for designing new advanced materials and devices.

  4. Performance of Cooperative Eigenvalue Spectrum Sensing with a Realistic Receiver Model under Impulsive Noise

    Directory of Open Access Journals (Sweden)

    Dayan A. Guimarães

    2013-01-01

    Full Text Available In this paper we present a unified comparison of the performance of four detection techniques for centralized data-fusion cooperative spectrum sensing in cognitive radio networks under impulsive noise, namely, the eigenvalue-based generalized likelihood ratio test (GLRT, the maximum-minimum eigenvalue detection (MMED, the maximum eigenvalue detection (MED, and the energy detection (ED. We consider two system models: an implementation-oriented model that includes the most relevant signal processing tasks realized by a real cognitive radio receiver, and the theoretical model conventionally adopted in the literature. We show that under the implementation-oriented model, GLRT and MMED are quite robust under impulsive noise, whereas the performance of MED and ED is drastically degraded. We also show that performance under the conventional model can be too pessimistic if impulsive noise is present, whereas it can be too optimistic in the absence of this impairment. We also discuss the fact that impulsive noise is not such a severe problem when we take into account the more realistic implementation-oriented model.

  5. Acoustic mode measurements in the inlet of a model turbofan using a continuously rotating rake - Data collection/analysis techniques

    Science.gov (United States)

    Hall, David G.; Heidelberg, Laurence; Konno, Kevin

    1993-01-01

    The rotating microphone measurement technique and data analysis procedures are documented which are used to determine circumferential and radial acoustic mode content in the inlet of the Advanced Ducted Propeller (ADP) model. Circumferential acoustic mode levels were measured at a series of radial locations using the Doppler frequency shift produced by a rotating inlet microphone probe. Radial mode content was then computed using a least squares curve fit with the measured radial distribution for each circumferential mode. The rotating microphone technique is superior to fixed-probe techniques because it results in minimal interference with the acoustic modes generated by rotor-stator interaction. This effort represents the first experimental implementation of a measuring technique developed by T. G. Sofrin. Testing was performed in the NASA Lewis Low Speed Anechoic Wind Tunnel at a simulated takeoff condition of Mach 0.2. The design is included of the data analysis software and the performance of the rotating rake apparatus. The effect of experiment errors is also discussed.

  6. Acoustic mode measurements in the inlet of a model turbofan using a continuously rotating rake: Data collection/analysis techniques

    Science.gov (United States)

    Hall, David G.; Heidelberg, Laurence; Konno, Kevin

    1993-01-01

    The rotating microphone measurement technique and data analysis procedures are documented which are used to determine circumferential and radial acoustic mode content in the inlet of the Advanced Ducted Propeller (ADP) model. Circumferential acoustic mode levels were measured at a series of radial locations using the Doppler frequency shift produced by a rotating inlet microphone probe. Radial mode content was then computed using a least squares curve fit with the measured radial distribution for each circumferential mode. The rotating microphone technique is superior to fixed-probe techniques because it results in minimal interference with the acoustic modes generated by rotor-stator interaction. This effort represents the first experimental implementation of a measuring technique developed by T. G. Sofrin. Testing was performed in the NASA Lewis Low Speed Anechoic Wind Tunnel at a simulated takeoff condition of Mach 0.2. The design is included of the data analysis software and the performance of the rotating rake apparatus. The effect of experiment errors is also discussed.

  7. Simple computer program to model 3-dimensional underground heat flow with realistic boundary conditions

    Science.gov (United States)

    Metz, P. D.

    A FORTRAN computer program called GROCS (GRound Coupled Systems) has been developed to study 3-dimensional underground heat flow. Features include the use of up to 30 finite elements or blocks of Earth which interact via finite difference heat flow equations and a subprogram which sets realistic time and depth dependent boundary conditions. No explicit consideration of mositure movement or freezing is given. GROCS has been used to model the thermal behavior of buried solar heat storage tanks (with and without insulation) and serpentine pipe fields for solar heat pump space conditioning systems. The program is available independently or in a form compatible with specially written TRNSYS component TYPE subroutines. The approach taken in the design of GROCS, the mathematics contained and the program architecture, are described. Then, the operation of the stand-alone version is explained. Finally, the validity of GROCS is discussed.

  8. Ab Initio No-Core Shell Model Calculations Using Realistic Two- and Three-Body Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Navratil, P; Ormand, W E; Forssen, C; Caurier, E

    2004-11-30

    There has been significant progress in the ab initio approaches to the structure of light nuclei. One such method is the ab initio no-core shell model (NCSM). Starting from realistic two- and three-nucleon interactions this method can predict low-lying levels in p-shell nuclei. In this contribution, we present a brief overview of the NCSM with examples of recent applications. We highlight our study of the parity inversion in {sup 11}Be, for which calculations were performed in basis spaces up to 9{Dirac_h}{Omega} (dimensions reaching 7 x 10{sup 8}). We also present our latest results for the p-shell nuclei using the Tucson-Melbourne TM three-nucleon interaction with several proposed parameter sets.

  9. A realistic quantum capacitance model for quantum Hall edge state based Fabry-Pérot interferometers

    Science.gov (United States)

    Kilicoglu, O.; Eksi, D.; Siddiki, A.

    2017-01-01

    In this work, the classical and the quantum capacitances are calculated for a Fabry-Pérot interferometer operating in the integer quantized Hall regime. We first consider a rotationally symmetric electrostatic confinement potential and obtain the widths and the spatial distribution of the insulating (incompressible) circular strips using a charge density profile stemming from self-consistent calculations. Modelling the electrical circuit of capacitors composed of metallic gates and incompressible/compressible strips, we investigate the conditions to observe Aharonov-Bohm (quantum mechanical phase dependent) and Coulomb blockade (capacitive coupling dependent) effects reflected in conductance oscillations. In a last step, we solve the Schrödinger and the Poisson equations self-consistently in a numerical manner taking into account realistic experimental geometries. We find that, describing the conductance oscillations either by Aharanov-Bohm or Coulomb blockade strongly depends on sample properties also other than size, therefore, determining the origin of these oscillations requires further experimental and theoretical investigation.

  10. Numerical models for stationary superfluid neutron stars in general relativity with realistic equations of state

    CERN Document Server

    Sourie, Aurélien; Novak, Jérôme

    2016-01-01

    We present a numerical model for uniformly rotating superfluid neutron stars, for the first time with realistic microphysics including entrainment, in a fully general relativistic framework. We compute stationary and axisymmetric configurations of neutron stars composed of two fluids, namely superfluid neutrons and charged particles (protons and electrons), rotating with different rates around a common axis. Both fluids are coupled by entrainment, a non-dissipative interaction which in case of a non-vanishing relative velocity between the fluids, causes the fluid momenta being not aligned with the respective fluid velocities. We extend the formalism by Comer and Joynt (2003) in order to calculate the equation of state (EoS) and entrainment parameters for an arbitrary relative velocity. The resulting entrainment matrix fulfills all necessary sum rules and in the limit of small relative velocity our results agree with Fermi liquid theory ones, derived to lowest order in the velocity. This formalism is applied t...

  11. Study of airflow during respiratory cycle in semi-realistic model of human tracheobronchial tree

    Science.gov (United States)

    Elcner, Jakub; Zaremba, M.; Maly, M.; Jedelsky, J.; Lizal, F.; Jicha, M.

    2016-06-01

    This article deals with study of airflow under breathing process, which is characteristic by unsteady behavior. Simulations provided by computational fluid dynamics (CFD) was compared with experiments performed on similar geometry of human upper airways. This geometry was represented by mouth cavity of realistic shape connected to an idealized tracheobronchial tree up to fourth generation of branching. Commercial CFD software Star-CCM+ was used to calculate airflow inside investigated geometry and method of Reynolds averaging of Navier-Stokes equations was used for subscribing the turbulent behavior through model geometry. Conditions corresponding to resting state were considered. Comparisons with experiments were provided on several points through trachea and bronchial tree and results with respect to inspiratory and respiratory part of breathing cycle was discussed.

  12. Software phantom with realistic speckle modeling for validation of image analysis methods in echocardiography

    Science.gov (United States)

    Law, Yuen C.; Tenbrinck, Daniel; Jiang, Xiaoyi; Kuhlen, Torsten

    2014-03-01

    Computer-assisted processing and interpretation of medical ultrasound images is one of the most challenging tasks within image analysis. Physical phenomena in ultrasonographic images, e.g., the characteristic speckle noise and shadowing effects, make the majority of standard methods from image analysis non optimal. Furthermore, validation of adapted computer vision methods proves to be difficult due to missing ground truth information. There is no widely accepted software phantom in the community and existing software phantoms are not exible enough to support the use of specific speckle models for different tissue types, e.g., muscle and fat tissue. In this work we propose an anatomical software phantom with a realistic speckle pattern simulation to _ll this gap and provide a exible tool for validation purposes in medical ultrasound image analysis. We discuss the generation of speckle patterns and perform statistical analysis of the simulated textures to obtain quantitative measures of the realism and accuracy regarding the resulting textures.

  13. Modelling the long-term morphological evolution of a coupled open coast, inlet and estuary system to explore climate change impacts

    Science.gov (United States)

    van Maanen, Barend; Walkden, Mike; Barnes, John; Nicholls, Robert

    2016-04-01

    Coastal and shoreline management increasingly needs to account for morphological change occurring at decadal to centennial timescales. Critical aspects of geomorphic behaviour at these temporal scales emerge at a system level, such that accounting for the feedbacks between different landform components is of key importance. In this study we develop new methods to simulate the large-scale evolution of a coupled open coast - inlet - estuary system, allowing us to explore the system's response to climate change impacts and management interventions. The system explored here encompasses the Deben estuary (eastern England) and its adjacent shorelines. The estuary itself mainly consists of finer sediments. Sediments throughout the inlet, on the other hand, including the ebb-tidal delta itself, comprise a mixture of gravel and sand. The ebb-tidal shoals and sediment bypassing show broadly cyclic behaviour on a 10 to 30 year timescale. Neighbouring beaches consist of mixed sediment and are partially backed up by sedimentary cliffs, the behaviour of which is potentially influenced by the sediment bypassing at the inlet. In addition, the open coast has undergone major transformations as a result of numerous sea defences which have altered sediment availability and supply. The interlinked behaviour of this system is approached by coupling a new inlet model (MESO_i) with an existing, and recently extended, model for the open coast (SCAPE+). MESOi simulates the evolution at the mouth of the Deben at an aggregated scale, conceptualizing the inlet by different geomorphic features that are characterized mainly by their volume. The behaviour of the inlet shoals is influenced by the estuarine tidal prism, linking estuarine processes with inlet dynamics. SCAPE+ computes the shaping of the shore profile and has proven capable of providing valuable information in terms of decadal evolution and related cliff recession rates. Simulations conducted with this composition of models highlight

  14. Simulating realistic disc galaxies with a novel sub-resolution ISM model

    Science.gov (United States)

    Murante, Giuseppe; Monaco, Pierluigi; Borgani, Stefano; Tornatore, Luca; Dolag, Klaus; Goz, David

    2015-02-01

    We present results of cosmological simulations of disc galaxies carried out with the GADGET-3 TreePM+SPH code, where star formation and stellar feedback are described using our MUlti Phase Particle Integrator model. This description is based on a simple multiphase model of the interstellar medium at unresolved scales, where mass and energy flows among the components are explicitly followed by solving a system of ordinary differential equations. Thermal energy from supernovae is injected into the local hot phase, so as to avoid that it is promptly radiated away. A kinetic feedback prescription generates the massive outflows needed to avoid the overproduction of stars. We use two sets of zoomed-in initial conditions of isolated cosmological haloes with masses (2-3) × 1012 M⊙, both available at several resolution levels. In all cases we obtain spiral galaxies with small bulge-over-total stellar mass ratios (B/T ˜ 0.2), extended stellar and gas discs, flat rotation curves and realistic values of stellar masses. Gas profiles are relatively flat, molecular gas is found to dominate at the centre of galaxies, with star formation rates following the observed Schmidt-Kennicutt relation. Stars kinematically belonging to the bulge form early, while disc stars show a clear inside-out formation pattern and mostly form after redshift z = 2. However, the baryon conversion efficiencies in our simulations differ from the relation given by Moster et al. at a 3σ level, thus indicating that our stellar discs are still too massive for the dark matter halo in which they reside. Results are found to be remarkably stable against resolution. This further demonstrates the feasibility of carrying out simulations producing a realistic population of galaxies within representative cosmological volumes, at a relatively modest resolution.

  15. Multiscale modelling as a tool to prescribe realistic boundary conditions for the study of surgical procedures.

    Science.gov (United States)

    Laganà, K; Dubini, G; Migliavacca, F; Pietrabissa, R; Pennati, G; Veneziani, A; Quarteroni, A

    2002-01-01

    This work was motivated by the problems of analysing detailed 3D models of vascular districts with complex anatomy. It suggests an approach to prescribing realistic boundary conditions to use in order to obtain information on local as well as global haemodynamics. A method was developed which simultaneously solves Navier-Stokes equations for local information and a non-linear system of ordinary differential equations for global information. This is based on the principle that an anatomically detailed 3D model of a cardiovascular district can be achieved by using the finite element method. In turn the finite element method requires a specific boundary condition set. The approach outlined in this work is to include the system of ordinary differential equations in the boundary condition set. Such a multiscale approach was first applied to two controls: (i) a 3D model of a straight tube in a simple hydraulic network and (ii) a 3D model of a straight coronary vessel in a lumped-parameter model of the cardiovascular system. The results obtained are very close to the solutions available for the pipe geometry. This paper also presents preliminary results from the application of the methodology to a particular haemodynamic problem: namely the fluid dynamics of a systemic-to-pulmonary shunt in paediatric cardiac surgery.

  16. Modeling shortest path selection of the ant Linepithema humile using psychophysical theory and realistic parameter values.

    Science.gov (United States)

    von Thienen, Wolfhard; Metzler, Dirk; Witte, Volker

    2015-05-07

    The emergence of self-organizing behavior in ants has been modeled in various theoretical approaches in the past decades. One model explains experimental observations in which Argentine ants (Linepithema humile) selected the shorter of two alternative paths from their nest to a food source (shortest path experiments). This model serves as an important example for the emergence of collective behavior and self-organization in biological systems. In addition, it inspired the development of computer algorithms for optimization problems called ant colony optimization (ACO). In the model, a choice function describing how ants react to different pheromone concentrations is fundamental. However, the parameters of the choice function were not deduced experimentally but freely adapted so that the model fitted the observations of the shortest path experiments. Thus, important knowledge was lacking about crucial model assumptions. A recent study on the Argentine ant provided this information by measuring the response of the ants to varying pheromone concentrations. In said study, the above mentioned choice function was fitted to the experimental data and its parameters were deduced. In addition, a psychometric function was fitted to the data and its parameters deduced. Based on these findings, it is possible to test the shortest path model by applying realistic parameter values. Here we present the results of such tests using Monte Carlo simulations of shortest path experiments with Argentine ants. We compare the choice function and the psychometric function, both with parameter values deduced from the above-mentioned experiments. Our results show that by applying the psychometric function, the shortest path experiments can be explained satisfactorily by the model. The study represents the first example of how psychophysical theory can be used to understand and model collective foraging behavior of ants based on trail pheromones. These findings may be important for other

  17. Modelling realistic horizontal branch morphologies and their impact on spectroscopic ages of unresolved stellar systems

    Science.gov (United States)

    Percival, Susan M.; Salaris, Maurizio

    2011-04-01

    The presence of an extended blue horizontal branch (HB) in a stellar population is known to affect the age inferred from spectral fitting to stellar population synthesis models. This is due to the hot blue component which increases the strength of the Balmer lines and can make an old population look spuriously young. However, most population synthesis models still rely on theoretical isochrones, which do not include realistic modelling of extended HBs. In this work, we create detailed models for a range of old simple stellar populations (SSPs), with metallicities ranging from [Fe/H]=-1.3 to solar, to create a variety of realistic HB morphologies, from extended red clumps, to extreme blue HBs. We achieve this by utilizing stellar tracks from the BaSTI data base and implementing a different mass-loss prescription for each SSP created. This includes setting an average mass and a Gaussian spread in masses of individual stars coming on to the zero-age HB for each model, and hence resulting in different HB morphologies. We find that, for each metallicity, there is some HB morphology which maximizes Hβ, making an underlying 14-Gyr population look ˜5-6 Gyr old for the low- and intermediate-metallicity cases, and as young as 2 Gyr in the case of the solar metallicity SSP. We explore whether there are any spectral indices capable of breaking the degeneracy between an old SSP with extended blue HB and a truly young or intermediate-age SSP, and find that the Ca II index of Rose and the strength of the Mg II doublet at 2800 Å are promising candidates, in combination with Hβ and other metallicity indicators, such as Mgb and Fe5406. We also run Monte Carlo simulations to investigate the level of statistical fluctuations in the spectra of typical stellar clusters. We find that fluctuations in spectral indices are significant even for average to large globular clusters and that various spectral indices are affected in different ways, which has implications for full

  18. Evaluation of three-dimensional anisotropic head model for mapping realistic electromagnetic fields of brain tissues

    Directory of Open Access Journals (Sweden)

    Woo Chul Jeong

    2015-08-01

    Full Text Available Electromagnetic fields provide fundamental data for the imaging of electrical tissue properties, such as conductivity and permittivity, in recent magnetic resonance (MR-based tissue property mapping. The induced voltage, current density, and magnetic flux density caused by externally injected current are critical factors for determining the image quality of electrical tissue conductivity. As a useful tool to identify bio-electromagnetic phenomena, precise approaches are required to understand the exact responses inside the human body subject to an injected currents. In this study, we provide the numerical simulation results of electromagnetic field mapping of brain tissues using a MR-based conductivity imaging method. First, we implemented a realistic three-dimensional human anisotropic head model using high-resolution anatomical and diffusion tensor MR images. The voltage, current density, and magnetic flux density of brain tissues were imaged by injecting 1 mA of current through pairs of electrodes on the surface of our head model. The current density map of anisotropic brain tissues was calculated from the measured magnetic flux density based on the linear relationship between the water diffusion tensor and the electrical conductivity tensor. Comparing the current density to the previous isotropic model, the anisotropic model clearly showed the differences between the brain tissues. This originates from the enhanced signals by the inherent conductivity contrast as well as the actual tissue condition resulting from the injected currents.

  19. Evaluation of three-dimensional anisotropic head model for mapping realistic electromagnetic fields of brain tissues

    Science.gov (United States)

    Jeong, Woo Chul; Wi, Hun; Sajib, Saurav Z. K.; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

    2015-08-01

    Electromagnetic fields provide fundamental data for the imaging of electrical tissue properties, such as conductivity and permittivity, in recent magnetic resonance (MR)-based tissue property mapping. The induced voltage, current density, and magnetic flux density caused by externally injected current are critical factors for determining the image quality of electrical tissue conductivity. As a useful tool to identify bio-electromagnetic phenomena, precise approaches are required to understand the exact responses inside the human body subject to an injected currents. In this study, we provide the numerical simulation results of electromagnetic field mapping of brain tissues using a MR-based conductivity imaging method. First, we implemented a realistic three-dimensional human anisotropic head model using high-resolution anatomical and diffusion tensor MR images. The voltage, current density, and magnetic flux density of brain tissues were imaged by injecting 1 mA of current through pairs of electrodes on the surface of our head model. The current density map of anisotropic brain tissues was calculated from the measured magnetic flux density based on the linear relationship between the water diffusion tensor and the electrical conductivity tensor. Comparing the current density to the previous isotropic model, the anisotropic model clearly showed the differences between the brain tissues. This originates from the enhanced signals by the inherent conductivity contrast as well as the actual tissue condition resulting from the injected currents.

  20. Investigations of sensitivity and resolution of ECG and MCG in a realistically shaped thorax model.

    Science.gov (United States)

    Mäntynen, Ville; Konttila, Teijo; Stenroos, Matti

    2014-12-07

    Solving the inverse problem of electrocardiography (ECG) and magnetocardiography (MCG) is often referred to as cardiac source imaging. Spatial properties of ECG and MCG as imaging systems are, however, not well known. In this modelling study, we investigate the sensitivity and point-spread function (PSF) of ECG, MCG, and combined ECG+MCG as a function of source position and orientation, globally around the ventricles: signal topographies are modelled using a realistically-shaped volume conductor model, and the inverse problem is solved using a distributed source model and linear source estimation with minimal use of prior information. The results show that the sensitivity depends not only on the modality but also on the location and orientation of the source and that the sensitivity distribution is clearly reflected in the PSF. MCG can better characterize tangential anterior sources (with respect to the heart surface), while ECG excels with normally-oriented and posterior sources. Compared to either modality used alone, the sensitivity of combined ECG+MCG is less dependent on source orientation per source location, leading to better source estimates. Thus, for maximal sensitivity and optimal source estimation, the electric and magnetic measurements should be combined.

  1. Compression, Modeling, and Real-Time Rendering of Realistic Materials and Objects

    OpenAIRE

    Menzel, Nicolas

    2012-01-01

    The realism of a scene basically depends on the quality of the geometry, the illumination and the materials that are used. Whereas many sources for the creation of three-dimensional geometry exist and numerous algorithms for the approximation of global illumination were presented, the acquisition and rendering of realistic materials remains a challenging problem. Realistic materials are very important in computer graphics, because...

  2. Realistic modeling of seismic input for megacities and large urban areas

    Science.gov (United States)

    Panza, G. F.; Unesco/Iugs/Igcp Project 414 Team

    2003-04-01

    The project addressed the problem of pre-disaster orientation: hazard prediction, risk assessment, and hazard mapping, in connection with seismic activity and man-induced vibrations. The definition of realistic seismic input has been obtained from the computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different source and structural models. The innovative modeling technique, that constitutes the common tool to the entire project, takes into account source, propagation and local site effects. This is done using first principles of physics about wave generation and propagation in complex media, and does not require to resort to convolutive approaches, that have been proven to be quite unreliable, mainly when dealing with complex geological structures, the most interesting from the practical point of view. In fact, several techniques that have been proposed to empirically estimate the site effects using observations convolved with theoretically computed signals corresponding to simplified models, supply reliable information about the site response to non-interfering seismic phases. They are not adequate in most of the real cases, when the seismic sequel is formed by several interfering waves. The availability of realistic numerical simulations enables us to reliably estimate the amplification effects even in complex geological structures, exploiting the available geotechnical, lithological, geophysical parameters, topography of the medium, tectonic, historical, palaeoseismological data, and seismotectonic models. The realistic modeling of the ground motion is a very important base of knowledge for the preparation of groundshaking scenarios that represent a valid and economic tool for the seismic microzonation. This knowledge can be very fruitfully used by civil engineers in the design of new seismo-resistant constructions and in the reinforcement of the existing built environment, and, therefore

  3. First synchronous realistic simulations of Antarctic and Greenland SMB in a fully coupled climate model

    Science.gov (United States)

    Lenaerts, J.; van Kampenhout, L.; Lipscomb, W. H.; Gettelman, A.; van den Broeke, M.; Sacks, W.; Fyke, J. G.; Vizcaino, M.; Löfverström, M.

    2015-12-01

    Here we use the global, coupled ocean-atmosphere-land Community Earth System Model (CESM) at a 1o degree horizontal resolution to simulate recent past (1850-now) and future (21st century) Greenland and Antarctic ice sheet SMB in tandem. To that end, we have recently improved the representation of firn in CESM. We increased the vertical thickness of snow, which enhances the buffering of meltwater through refreezing, and firn density, to allow for wind-induced snow compaction. Other model improvements focused on atmospheric clouds; the most recent CESM atmosphere model allows for more liquid water in clouds, which increases positive longwave cloud forcing, and has profound and beneficial impact on the ice sheet surface radiation balance. In this contribution, we will show that the above improvements enable a realistic CESM simulation of both Greenland and Antarctic SMB. This allows for analysis of future evolution of ice sheet SMB and the interactions between ice sheets and other components of the climate system.

  4. Random vs realistic amorphous carbon models for high resolution microscopy and electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ricolleau, C., E-mail: Christian.Ricolleau@univ-paris-diderot.fr; Alloyeau, D. [Laboratoire Matériaux et Phénomènes Quantiques, CNRS-UMR 7162, Université Paris Diderot-Paris 7, Case 7021, 75205 Paris Cedex 13 (France); Le Bouar, Y.; Amara, H.; Landon-Cardinal, O. [Laboratoire d' Etude des Microstructures, UMR CNRS/Onera, 29, avenue de la Division Leclerc, 92322 Châtillon (France)

    2013-12-07

    Amorphous carbon and amorphous materials in general are of particular importance for high resolution electron microscopy, either for bulk materials, generally covered with an amorphous layer when prepared by ion milling techniques, or for nanoscale objects deposited on amorphous substrates. In order to quantify the information of the high resolution images at the atomic scale, a structural modeling of the sample is necessary prior to the calculation of the electron wave function propagation. It is thus essential to be able to reproduce the carbon structure as close as possible to the real one. The approach we propose here is to simulate a realistic carbon from an energetic model based on the tight-binding approximation in order to reproduce the important structural properties of amorphous carbon. At first, we compare this carbon with the carbon obtained by randomly generating the carbon atom positions. In both cases, we discuss the limit thickness of the phase object approximation. In a second step, we show the influence of both carbons models on (i) the contrast of Cu, Ag, and Au single atoms deposited on carbon and (ii) the determination of the long-range order parameter in CoPt bimetallic nanoalloys.

  5. Time variation of the fine structure constant α from realistic models of Oklo reactors.

    Science.gov (United States)

    Gould, C. R.; Sharapov, E. I.; Lamoreaux, S. K.

    2006-11-01

    The topic of whether the fundamental constants of nature vary with time has been a subject of great interest since Dirac originally proposed the possibility that GN˜1/tuniverse. Recent observations of absorption spectra lines from distant quasars appeared to indicate a possible increase in the fine structure constant α over ten billion years. Contrarily, analyses of the time evolution of α from Oklo natural nuclear reactor data have yielded inconsistent results, some indicating a decrease over two billion years while others indicated no change. We have used known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Reactors RZ2 and RZ10 were modeled with MCNP and the resulting neutron spectra were used to calculate the change in the ^149Sm capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. Our study resolves the contradictory situation with previous Oklo α-results. Our suggested 2 σ bound on a possible time variation of α over two billion years is stringent: -0.11 <=δαα <=0.24, in units of 10-7, but model dependent in that it assumes only α has varied over time.

  6. Neutrino Mass and Proton Decay in a Realistic Supersymmetric SO(10) Model

    CERN Document Server

    Severson, Matthew

    2016-01-01

    This work presents a complete analysis of fermion fitting and proton decay in a SUSY $SO(10)$ model previously suggested by Dutta, Mimura, and Mohapatra. A key question in any grand unified theory is whether it satisfies the experimental lower limits on proton partial lifetimes. In generic models, substantial fine-tuning is required among GUT-scale parameters to satisfy the limits. In the proposed model, the ${\\bf 10}$, $\\overline{\\bf{126}}$, and ${\\bf 120}$ Yukawa couplings contributing to fermion masses have restricted textures intended to give favorable results for proton lifetime, while still giving rise to a realistic fermion sector, without the need for fine-tuning, even for large $\\tan\\beta$, and for either type-I or type-II dominance in the neutrino mass matrix. In this thesis, I investigate the above hypothesis at a strict numerical level of scrutiny; I obtain a valid fit for the entire fermion sector for both types of seesaw dominance, including $\\theta_{13}$ in good agreement with the most recent d...

  7. Realistic modeling of the pulse profile of PSR J0737-3039A

    Energy Technology Data Exchange (ETDEWEB)

    Perera, B. B. P.; Kim, C.; McLaughlin, M. A. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Ferdman, R. D. [Department of Physics, McGill University, Ernest Rutherford Physics Building, 3600 University Street, Montreal, QC H3A 2T8 (Canada); Kramer, M.; Freire, P. C. C. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Stairs, I. H. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1 (Canada); Possenti, A. [INAF-Osservatorio Astronomica di Cagliari, Loc. Poggio dei Pini, Strada 54, I-09012 Capoterra (Italy)

    2014-05-20

    The Double Pulsar, PSR J0737-3039A/B, is a unique system in which both neutron stars have been detected as radio pulsars. As shown in Ferdman et al., there is no evidence for pulse profile evolution of the A pulsar, and the geometry of the pulsar was fit well with a double-pole circular radio beam model. Assuming a more realistic polar cap model with a vacuum retarded dipole magnetosphere configuration including special relativistic effects, we create synthesized pulse profiles for A given the best-fit geometry from the simple circular beam model. By fitting synthesized pulse profiles to those observed from pulsar A, we constrain the geometry of the radio beam, namely the half-opening angle and the emission altitude, to be ∼30° and ∼10 neutron star radii, respectively. Combining the observational constraints of PSR J0737-3039A/B, we are able to construct the full three-dimensional orbital geometry of the Double Pulsar. The relative angle between the spin axes of the two pulsars (Δ{sub S}) is estimated to be ∼(138° ± 5°) at the current epoch and will likely remain constant until tidal interactions become important in ∼85 Myr, at merger.

  8. Realistic Modeling of the Pulse Profile of PSR J$0737$$-$$3039$A

    CERN Document Server

    Perera, B B P; McLaughlin, M A; Ferdman, R D; Kramer, M; Stairs, I H; Freire, P C C; Possenti, A

    2014-01-01

    The Double Pulsar, PSR J$0737$$-$$3039$A/B, is a unique system in which both neutron stars have been detected as radio pulsars. As shown in Ferdman et al., there is no evidence for pulse profile evolution of the A pulsar, and the geometry of the pulsar was fit well with a double-pole circular radio beam model. Assuming a more realistic polar cap model with a vacuum retarded dipole magnetosphere configuration including special relativistic effects, we create synthesized pulse profiles for A given the best-fit geometry from the simple circular beam model. By fitting synthesized pulse profiles to those observed from pulsar A, we constrain the geometry of the radio beam, namely the half-opening angle and the emission altitude, to be $30^\\circ$ and $10$ neutron star radii, respectively. Combining the observational constraints of PSR J$0737$$-$$3039$A/B, we are able to construct the full three-dimensional orbital geometry of the Double Pulsar. The relative angle between the spin axes of the two pulsars ($\\Delta_S$)...

  9. Smart-DS: Synthetic Models for Advanced, Realistic Testing: Distribution Systems and Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, Venkat K [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Palmintier, Bryan S [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Hodge, Brian S [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Hale, Elaine T [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Elgindy, Tarek [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bugbee, Bruce [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rossol, Michael N [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Lopez, Anthony J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Krishnamurthy, Dheepak [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Vergara, Claudio [MIT; Domingo, Carlos Mateo [IIT Comillas; Postigo, Fernando [IIT Comillas; de Cuadra, Fernando [IIT Comillas; Gomez, Tomas [IIT Comillas; Duenas, Pablo [MIT; Luke, Max [MIT; Li, Vivian [MIT; Vinoth, Mohan [GE Grid Solutions; Kadankodu, Sree [GE Grid Solutions

    2017-08-09

    The National Renewable Energy Laboratory (NREL) in collaboration with Massachusetts Institute of Technology (MIT), Universidad Pontificia Comillas (Comillas-IIT, Spain) and GE Grid Solutions, is working on an ARPA-E GRID DATA project, titled Smart-DS, to create: 1) High-quality, realistic, synthetic distribution network models, and 2) Advanced tools for automated scenario generation based on high-resolution weather data and generation growth projections. Through these advancements, the Smart-DS project is envisioned to accelerate the development, testing, and adoption of advanced algorithms, approaches, and technologies for sustainable and resilient electric power systems, especially in the realm of U.S. distribution systems. This talk will present the goals and overall approach of the Smart-DS project, including the process of creating the synthetic distribution datasets using reference network model (RNM) and the comprehensive validation process to ensure network realism, feasibility, and applicability to advanced use cases. The talk will provide demonstrations of early versions of synthetic models, along with the lessons learnt from expert engagements to enhance future iterations. Finally, the scenario generation framework, its development plans, and co-ordination with GRID DATA repository teams to house these datasets for public access will also be discussed.

  10. On the validation of a realistic model of mesoscale coastal circulation in the Western Iberian Peninsula

    Science.gov (United States)

    Dubert, Jesus; Cordeiro, Nuno; Nolasco, Rita

    2010-05-01

    Realistic simulations of the circulation off the Western Iberian Peninsula, for the period 2001-2009 are compared against satellite observations of sea surface temperature (SST), for the summer upwelling season. This was done by means of comparisons of climatological means of monthly sst, standard deviation, and monthly anomalies obtained from satellite, and from the numerical model. Also, the observed mesoscale structures like filaments, are also compared with those obtained with the model, for the same period. The model consists in a ROMS-AGRIF configuration at ~3km resolution, forced with 6h NCEP2 reanalysis and Quikscat forcing for winds for the referred period, in the presence of river inflow for the main rivers of the region. The boundary conditions are obtained by offline nesting from a configuration of a larger domain, forced in the same way, and offshore Levitus climatological boundaries. The filament characterization for the satellite data, and the outputs of the numerical model, was done based on an automatic data treatment, which allows to study the filaments seasonal and interannual variability for the studied period. It was also made a study and a discussion of the surface climatology based on the satellite images and the model, in order to characterize, the surface temperature field, the monthly means, standard deviation and the deviations from the mean. In order to explain the observed and modelled anomalies, NCEP winds reanalysis are used in several points in the studied domain. The main purpose of this study is a step forward in the validation of the numerical configuration resolving mesoscale in the Western Iberian Peninsula, and to is to determine whether or not the model is able to reproduce the observed mesoscale features, the monthly anomalies of sst, and the monthly climatology.

  11. Explicit all-atom modeling of realistically sized ligand-capped nanocrystals.

    Science.gov (United States)

    Kaushik, Ananth P; Clancy, Paulette

    2012-03-21

    We present a study of an explicit all-atom representation of nanocrystals of experimentally relevant sizes (up to 6 nm), "capped" with alkyl chain ligands, in vacuum. We employ all-atom molecular dynamics simulation methods in concert with a well-tested intermolecular potential model, MM3 (molecular mechanics 3), for the studies presented here. These studies include determining the preferred conformation of an isolated single nanocrystal (NC), pairs of isolated NCs, and (presaging studies of superlattice arrays) unit cells of NC superlattices. We observe that very small NCs (3 nm) behave differently in a superlattice as compared to larger NCs (6 nm and above) due to the conformations adopted by the capping ligands on the NC surface. Short ligands adopt a uniform distribution of orientational preferences, including some that lie against the face of the nanocrystal. In contrast, longer ligands prefer to interdigitate. We also study the effect of changing ligand length and ligand coverage on the NCs on the preferred ligand configurations. Since explicit all-atom modeling constrains the maximum system size that can be studied, we discuss issues related to coarse-graining the representation of the ligands, including a comparison of two commonly used coarse-grained models. We find that care has to be exercised in the choice of coarse-grained model. The data provided by these realistically sized ligand-capped NCs, determined using explicit all-atom models, should serve as a reference standard for future models of coarse-graining ligands using united atom models, especially for self-assembly processes.

  12. Explicit all-atom modeling of realistically sized ligand-capped nanocrystals

    KAUST Repository

    Kaushik, Ananth P.

    2012-01-01

    We present a study of an explicit all-atom representation of nanocrystals of experimentally relevant sizes (up to 6 nm), capped with alkyl chain ligands, in vacuum. We employ all-atom molecular dynamics simulation methods in concert with a well-tested intermolecular potential model, MM3 (molecular mechanics 3), for the studies presented here. These studies include determining the preferred conformation of an isolated single nanocrystal (NC), pairs of isolated NCs, and (presaging studies of superlattice arrays) unit cells of NC superlattices. We observe that very small NCs (3 nm) behave differently in a superlattice as compared to larger NCs (6 nm and above) due to the conformations adopted by the capping ligands on the NC surface. Short ligands adopt a uniform distribution of orientational preferences, including some that lie against the face of the nanocrystal. In contrast, longer ligands prefer to interdigitate. We also study the effect of changing ligand length and ligand coverage on the NCs on the preferred ligand configurations. Since explicit all-atom modeling constrains the maximum system size that can be studied, we discuss issues related to coarse-graining the representation of the ligands, including a comparison of two commonly used coarse-grained models. We find that care has to be exercised in the choice of coarse-grained model. The data provided by these realistically sized ligand-capped NCs, determined using explicit all-atom models, should serve as a reference standard for future models of coarse-graining ligands using united atom models, especially for self-assembly processes. © 2012 American Institute of Physics.

  13. Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

    Science.gov (United States)

    Allan Brian G.; Owens, Lewis, R.

    2006-01-01

    This paper will investigate the validation of a NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as the baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a freestream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the length of the fan-face diameter. The numerical simulations with and without wind tunnel walls are performed, quantifying effects of the tunnel walls on the BLI inlet flow measurements. The wind tunnel test evaluated several different combinations of jet locations and mass flow rates as well as a vortex generator (VG) vane case. The numerical simulations will be performed on a single jet configuration for varying actuator mass flow rates at a fix inlet mass flow condition. Validation of the numerical simulations for the VG vane case will also be performed for varying inlet mass flow rates. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCPavg, very well for comparisons made within the designed operating range of the BLI inlet. However the CFD simulations did predict a total pressure recovery that was 0.01 lower than the experiment. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe

  14. Dynamic force matching: A method for constructing dynamical coarse-grained models with realistic time dependence

    Energy Technology Data Exchange (ETDEWEB)

    Davtyan, Aram; Dama, James F.; Voth, Gregory A. [Department of Chemistry, The James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Andersen, Hans C., E-mail: hca@stanford.edu [Department of Chemistry, Stanford University, Stanford, California 94305 (United States)

    2015-04-21

    the method provides realistic dynamical CG models that have non-Markovian or close to Markovian behavior that is consistent with the actual dynamical behavior of the all-atom system used to construct the CG model. Both the construction and the simulation of such a dynamic CG model have computational requirements that are similar to those of the corresponding MS-CG model and are good candidates for CG modeling of very large systems.

  15. Determination of an acoustic reflection coefficient at the inlet of a model gas turbine combustor for power generation

    Science.gov (United States)

    Song, W. J.; Cha, D. J.

    2017-01-01

    A phenomenon that potentially influences the reliability of power generation systems is the presence of thermo-acoustic oscillations in the combustion chamber of a land- based gas turbine. To develop specific measures that prevent the instability, it is essential to predict and/or evaluate the underlying physics of the thermo-acoustics, which requires the acoustic boundary condition at the exit of the burner, that is, at the inlet of the combustor. Here we report a procedure for calculating acoustic reflection coefficients at the burner exit by utilizing two microphone method (TMM) for dynamic pressure signals. The procedure has been verified by comparing its results with reported ones and further successfully employed to determine the acoustic boundary condition of the burner of a partially-premixed model gas turbine combustor.

  16. Atomic level insights into realistic molecular models of dendrimer-drug complexes through MD simulations

    Science.gov (United States)

    Jain, Vaibhav; Maiti, Prabal K.; Bharatam, Prasad V.

    2016-09-01

    Computational studies performed on dendrimer-drug complexes usually consider 1:1 stoichiometry, which is far from reality, since in experiments more number of drug molecules get encapsulated inside a dendrimer. In the present study, molecular dynamic (MD) simulations were implemented to characterize the more realistic molecular models of dendrimer-drug complexes (1:n stoichiometry) in order to understand the effect of high drug loading on the structural properties and also to unveil the atomistic level details. For this purpose, possible inclusion complexes of model drug Nateglinide (Ntg) (antidiabetic, belongs to Biopharmaceutics Classification System class II) with amine- and acetyl-terminated G4 poly(amidoamine) (G4 PAMAM(NH2) and G4 PAMAM(Ac)) dendrimers at neutral and low pH conditions are explored in this work. MD simulation analysis on dendrimer-drug complexes revealed that the drug encapsulation efficiency of G4 PAMAM(NH2) and G4 PAMAM(Ac) dendrimers at neutral pH was 6 and 5, respectively, while at low pH it was 12 and 13, respectively. Center-of-mass distance analysis showed that most of the drug molecules are located in the interior hydrophobic pockets of G4 PAMAM(NH2) at both the pH; while in the case of G4 PAMAM(Ac), most of them are distributed near to the surface at neutral pH and in the interior hydrophobic pockets at low pH. Structural properties such as radius of gyration, shape, radial density distribution, and solvent accessible surface area of dendrimer-drug complexes were also assessed and compared with that of the drug unloaded dendrimers. Further, binding energy calculations using molecular mechanics Poisson-Boltzmann surface area approach revealed that the location of drug molecules in the dendrimer is not the decisive factor for the higher and lower binding affinity of the complex, but the charged state of dendrimer and drug, intermolecular interactions, pH-induced conformational changes, and surface groups of dendrimer do play an

  17. Full waveform tomography for lithospheric imaging: results from a blind test in a realistic crustal model

    Science.gov (United States)

    Brenders, A. J.; Pratt, R. G.

    2007-01-01

    A comprehensive validation of 2-D, frequency-domain, acoustic wave-equation tomography was undertaken in a `blind test', using third-party, realistic, elastic wave-equation data. The synthetic 2-D, wide-angle seismic data were provided prior to a recent workshop on the methods of controlled source seismology; the true model was not revealed to the authors until after the presentation of our waveform tomography results. The original model was specified on a detailed grid with variable P-wave velocity, S-wave velocity, density and viscoelastic Q-factor structure, designed to simulate a section of continental crust 250 km long and 40 km deep. Synthetic vertical and horizontal component data were available for 51 shot locations (spaced every 5 km), recorded at 2779 receivers (spaced every 90 m), evenly spread along the surface of the model. The data contained energy from 0.2 to 15 Hz. Waveform tomography, a combination of traveltime tomography and 2-D waveform inversion of the early arrivals of the seismic waveforms, was used to recover crustal P-velocity structure from the vertical component data, using data from 51 sources, 1390 receivers and frequencies between 0.8 and 7.0 Hz. The waveform tomography result contained apparent structure at wavelength-scale resolution that was not evident on the traveltime tomography result. The predicted (acoustic) waveforms in the final result matched the original elastic data to a high degree of accuracy. During the workshop, the exact model was revealed; over much of the model the waveform tomography results provided a good correspondence with the true model, from large- to intermediate-(wavelength) scales, with a resolution limit on the order of 1 km. A significant, near-surface low-velocity zone, invisible to traveltime methods, was correctly recovered; the results also provided a high-resolution image of the complex structure of the entire crust, and the depth and nature of the crust-mantle transition. Some inaccuracies were

  18. Using coronal seismology to estimate the magnetic field strength in a realistic coronal model

    CERN Document Server

    Chen, Feng

    2015-01-01

    Coronal seismology is extensively used to estimate properties of the corona, e.g. the coronal magnetic field strength are derived from oscillations observed in coronal loops. We present a three-dimensional coronal simulation including a realistic energy balance in which we observe oscillations of a loop in synthesised coronal emission. We use these results to test the inversions based on coronal seismology. From the simulation of the corona above an active region we synthesise extreme ultraviolet (EUV) emission from the model corona. From this we derive maps of line intensity and Doppler shift providing synthetic data in the same format as obtained from observations. We fit the (Doppler) oscillation of the loop in the same fashion as done for observations to derive the oscillation period and damping time. The loop oscillation seen in our model is similar to imaging and spectroscopic observations of the Sun. The velocity disturbance of the kink oscillation shows an oscillation period of 52.5s and a damping tim...

  19. Simulating realistic disk galaxies with a novel sub-resolution ISM model

    CERN Document Server

    Murante, Giuseppe; Borgani, Stefano; Tornatore, Luca; Dolag, Klaus

    2014-01-01

    We present results of cosmological simulations of disk galaxies carried out with the GADGET-3 TreePM+SPH code, where star formation and stellar feedback are described using our MUlti Phase Particle Integrator (MUPPI) model. This description is based on simple multi-phase model of the interstellar medium at unresolved scales, where mass and energy flows among the components are explicitly followed by solving a system of ordinary differential equations. Thermal energy from SNe is injected into the local hot phase, so as to avoid that it is promptly radiated away. A kinetic feedback prescription generates the massive outflows needed to avoid the over-production of stars. We use two sets of zoomed-in initial conditions of isolated cosmological halos with masses (2-3) * 10^{12} Msun, both available at several resolution levels. In all cases we obtain spiral galaxies with small bulge-over-total stellar mass ratios (B/T \\approx 0.2), extended stellar and gas disks, flat rotation curves and realistic values of stella...

  20. Coset space dimensional reduction and classification of semi-realistic particle physics models

    Energy Technology Data Exchange (ETDEWEB)

    Douzas, G.; Grammatikopoulos, T. [National Technical University of Athens, Zografou Campus, 157 80 Zografou, Athens (Greece); Madore, J. [Laboratoire de Physique Theorique, Universite de Paris-Sud, Batiment 211, 91405 Orsay (France); Zoupanos, G.

    2008-04-15

    Starting from a Yang-Mills-Dirac theory defined in ten dimensions we classify the semi-realistic particle physics models resulting from their Forgacs-Manton dimensional reduction. The higher-dimensional gauge group is chosen to be E{sub 8}. This choice as well as the dimensionality of the space-time is suggested by the heterotic string theory. Furthermore, we assume that the space-time on which the theory is defined can be written in the compactified form M{sup 4} x B, with M{sup 4} the ordinary Minkowski spacetime and B=S/R a 6-dim homogeneous coset space. We constrain our investigation in those cases where the dimensional reduction leads in four dimensions to phenomenologically interesting and anomaly-free GUTs such as E{sub 6}, SO(10) and SU(5). However the four-dimensional surviving scalars transform in the fundamental of the resulting gauge group are not suitable for the superstrong symmetry breaking of the Standard Model. The main objective of our work is the investigation to which extent the latter can be achieved by employing the Wilson flux breaking mechanism. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  1. Towards Realistic Vehicular Network Modeling Using Planet-scale Public Webcams

    CERN Document Server

    Thakur, Gautam S; Ketabdar, Hamed; Helmy, Ahmed

    2011-01-01

    Realistic modeling of vehicular mobility has been particularly challenging due to a lack of large libraries of measurements in the research community. In this paper we introduce a novel method for large-scale monitoring, analysis, and identification of spatio-temporal models for vehicular mobility using the freely available online webcams in cities across the globe. We collect vehicular mobility traces from 2,700 traffic webcams in 10 different cities for several months and generate a mobility dataset of 7.5 Terabytes consisting of 125 million of images. To the best of our knowl- edge, this is the largest data set ever used in such study. To process and analyze this data, we propose an efficient and scalable algorithm to estimate traffic density based on background image subtraction. Initial results show that at least 82% of individual cameras with less than 5% deviation from four cities follow Loglogistic distribution and also 94% cameras from Toronto follow gamma distribution. The aggregate results from eac...

  2. A realistic pattern of fermion masses from a five-dimensional SO(10) model

    CERN Document Server

    Feruglio, Ferruccio; Vicino, Denise

    2015-01-01

    We provide a unified description of fermion masses and mixing angles in the framework of a supersymmetric grand unified SO(10) model with anarchic Yukawa couplings of order unity. The space-time is five dimensional and the extra flat spatial dimension is compactified on the orbifold $S^1/(Z_2 \\times Z_2')$, leading to Pati-Salam gauge symmetry on the boundary where Yukawa interactions are localised. The gauge symmetry breaking is completed by means of a rather economic scalar sector, avoiding the doublet-triplet splitting problem. The matter fields live in the bulk and their massless modes get exponential profiles, which naturally explain the mass hierarchy of the different fermion generations. Quarks and leptons properties are naturally reproduced by a mechanism, first proposed by Kitano and Li, that lifts the SO(10) degeneracy of bulk masses in terms of a single parameter. The model provides a realistic pattern of fermion masses and mixing angles for large values of $\\tan\\beta$. It favours normally ordered ...

  3. A novel CPU/GPU simulation environment for large-scale biologically realistic neural modeling.

    Science.gov (United States)

    Hoang, Roger V; Tanna, Devyani; Jayet Bray, Laurence C; Dascalu, Sergiu M; Harris, Frederick C

    2013-01-01

    Computational Neuroscience is an emerging field that provides unique opportunities to study complex brain structures through realistic neural simulations. However, as biological details are added to models, the execution time for the simulation becomes longer. Graphics Processing Units (GPUs) are now being utilized to accelerate simulations due to their ability to perform computations in parallel. As such, they have shown significant improvement in execution time compared to Central Processing Units (CPUs). Most neural simulators utilize either multiple CPUs or a single GPU for better performance, but still show limitations in execution time when biological details are not sacrificed. Therefore, we present a novel CPU/GPU simulation environment for large-scale biological networks, the NeoCortical Simulator version 6 (NCS6). NCS6 is a free, open-source, parallelizable, and scalable simulator, designed to run on clusters of multiple machines, potentially with high performance computing devices in each of them. It has built-in leaky-integrate-and-fire (LIF) and Izhikevich (IZH) neuron models, but users also have the capability to design their own plug-in interface for different neuron types as desired. NCS6 is currently able to simulate one million cells and 100 million synapses in quasi real time by distributing data across eight machines with each having two video cards.

  4. Modeling the Thermal Conductivity of Nanocomposites Using Monte-Carlo Methods and Realistic Nanotube Configurations

    Science.gov (United States)

    Bui, Khoa; Papavassiliou, Dimitrios

    2012-02-01

    The effective thermal conductivity (Keff) of carbon nanotube (CNT) composites is affected by the thermal boundary resistance (TBR) and by the dispersion pattern and geometry of the CNTs. We have previously modeled CNTs as straight cylinders and found that the TBR between CNTs (TBRCNT-CNT) can suppress Keff at high volume fractions of CNTs [1]. Effective medium theory results assume that the CNTs are in a perfect dispersion state and exclude the TBRCNT-CNT [2]. In this work, we report on the development of an algorithm for generating CNTs with worm-like geometry in 3D, and with different persistence lengths. These worm-like CNTs are then randomly placed in a periodic box representing a realistic state, since the persistence length of a CNT can be obtained from microscopic images. The use of these CNT geometries in conjunction with off-lattice Monte Carlo simulations [1] in order to study the effective thermal properties of nanocomposites will be discussed, as well as the effects of the persistence length on Keff and comparisons to straight cylinder models. References [1] K. Bui, B.P. Grady, D.V. Papavassiliou, Chem. Phys. Let., 508(4-6), 248-251, 2011 [2] C.W. Nan, G. Liu, Y. Lin, M. Li, App. Phys. Let., 85(16), 3549-3551, 2006

  5. Towards realistic representation of hydrological processes in integrated WRF-urban modeling system

    Science.gov (United States)

    Yang, Jiachuan; Wang, Zhi-hua; Chen, Fei; Miao, Shiguang; Tewari, Mukul; Georgescu, Matei

    2014-05-01

    To meet the demand of the ever-increasing urbanized global population, substantial conversion of natural landscapes to urban terrains is expected in the next few decades. The landscape modification will emerge as the source of many adverse effects that challenge the environmental sustainability of cities under changing climatic patterns. To address these adverse effects and to develop corresponding adaptation/mitigation strategies, physically-based single layer urban canopy model (SLUCM) has been developed and implemented into the Weather Research and Forecasting (WRF) platform. However, due to the lack of realistic representation of urban hydrological processes, simulation of urban climatology by current coupled WRF/SLUCM is inevitably inadequate. Aiming at improving the accuracy of simulations, in this study we implement physically-based parameterization of urban hydrological processes into the model, including (1) anthropogenic latent heat, (2) urban irrigation, (3) evaporation over water-holding engineered pavements, (4) urban oasis effect, and (5) green roof. In addition, we use an advanced Monte Carlo approach to quantify the sensitivity of urban hydrological modeling to parameter uncertainties. Evaluated against field observations at four major metropolitan areas, results show that the enhanced model is significantly improved in accurately predicting turbulent fluxes arising from built surfaces, especially the latent heat flux. Case studies show that green roof is capable of reducing urban surface temperature and sensible heat flux effectively, and modifying local and regional hydroclimate. Meanwhile, it is efficient in decreasing energy loading of buildings, not only cooling demand in summers but also heating demand in winters, through the combined evaporative cooling and insulation effect. Effectiveness of green roof is found to be limited by availability of water resources and highly sensitive to surface roughness heights. The enhanced WRF/SLUCM model

  6. Successful N{sub 2} leptogenesis with flavour coupling effects in realistic unified models

    Energy Technology Data Exchange (ETDEWEB)

    Bari, Pasquale Di; King, Stephen F. [Department of Physics and Astronomy, University of Southampton,Highfield, Southampton SO17 1BJ (United Kingdom)

    2015-10-02

    In realistic unified models involving so-called SO(10)-inspired patterns of Dirac and heavy right-handed (RH) neutrino masses, the lightest right-handed neutrino N{sub 1} is too light to yield successful thermal leptogenesis, barring highly fine tuned solutions, while the second heaviest right-handed neutrino N{sub 2} is typically in the correct mass range. We show that flavour coupling effects in the Boltzmann equations may be crucial to the success of such N{sub 2} dominated leptogenesis, by helping to ensure that the flavour asymmetries produced at the N{sub 2} scale survive N{sub 1} washout. To illustrate these effects we focus on N{sub 2} dominated leptogenesis in an existing model, the A to Z of flavour with Pati-Salam, where the neutrino Dirac mass matrix may be equal to an up-type quark mass matrix and has a particular constrained structure. The numerical results, supported by analytical insight, show that in order to achieve successful N{sub 2} leptogenesis, consistent with neutrino phenomenology, requires a “flavour swap scenario” together with a less hierarchical pattern of RH neutrino masses than naively expected, at the expense of some mild fine-tuning. In the considered A to Z model neutrino masses are predicted to be normal ordered, with an atmospheric neutrino mixing angle well into the second octant and the Dirac phase δ≃20{sup ∘}, a set of predictions that will be tested in the next years in neutrino oscillation experiments. Flavour coupling effects may be relevant for other SO(10)-inspired unified models where N{sub 2} leptogenesis is necessary.

  7. Fully 3D modeling of tokamak vertical displacement events with realistic parameters

    Science.gov (United States)

    Pfefferle, David; Ferraro, Nathaniel; Jardin, Stephen; Bhattacharjee, Amitava

    2016-10-01

    In this work, we model the complex multi-domain and highly non-linear physics of Vertical Displacement Events (VDEs), one of the most damaging off-normal events in tokamaks, with the implicit 3D extended MHD code M3D-C1. The code has recently acquired the capability to include finite thickness conducting structures within the computational domain. By exploiting the possibility of running a linear 3D calculation on top of a non-linear 2D simulation, we monitor the non-axisymmetric stability and assess the eigen-structure of kink modes as the simulation proceeds. Once a stability boundary is crossed, a fully 3D non-linear calculation is launched for the remainder of the simulation, starting from an earlier time of the 2D run. This procedure, along with adaptive zoning, greatly increases the efficiency of the calculation, and allows to perform VDE simulations with realistic parameters and high resolution. Simulations are being validated with NSTX data where both axisymmetric (toroidally averaged) and non-axisymmetric induced and conductive (halo) currents have been measured. This work is supported by US DOE Grant DE-AC02-09CH11466.

  8. A Novel CPU/GPU Simulation Environment for Large-Scale Biologically-Realistic Neural Modeling

    Directory of Open Access Journals (Sweden)

    Roger V Hoang

    2013-10-01

    Full Text Available Computational Neuroscience is an emerging field that provides unique opportunities to studycomplex brain structures through realistic neural simulations. However, as biological details are added tomodels, the execution time for the simulation becomes longer. Graphics Processing Units (GPUs are now being utilized to accelerate simulations due to their ability to perform computations in parallel. As such, they haveshown significant improvement in execution time compared to Central Processing Units (CPUs. Most neural simulators utilize either multiple CPUs or a single GPU for better performance, but still show limitations in execution time when biological details are not sacrificed. Therefore, we present a novel CPU/GPU simulation environment for large-scale biological networks,the NeoCortical Simulator version 6 (NCS6. NCS6 is a free, open-source, parallelizable, and scalable simula-tor, designed to run on clusters of multiple machines, potentially with high performance computing devicesin each of them. It has built-in leaky-integrate-and-fire (LIF and Izhikevich (IZH neuron models, but usersalso have the capability to design their own plug-in interface for different neuron types as desired. NCS6is currently able to simulate one million cells and 100 million synapses in quasi real time by distributing dataacross these heterogeneous clusters of CPUs and GPUs.

  9. Stimulation strength and focality of electroconvulsive therapy and magnetic seizure therapy in a realistic head model.

    Science.gov (United States)

    Lee, Won Hee; Lisanby, Sarah H; Laine, Andrew F; Peterchev, Angel V

    2014-01-01

    This study examines the characteristics of the electric field (E-field) induced in the brain by electroconvulsive therapy (ECT) and magnetic seizure therapy (MST). The electric field induced by five ECT electrode configurations (bilateral, bifrontal, right unilateral, focal electrically administered seizure therapy, and frontomedial) as well as an MST coil configuration (circular) was computed in an anatomically realistic finite element model of the human head. We computed the maps of the electric field strength relative to an estimated neural activation threshold, and used them to evaluate the stimulation strength and focality of the various ECT and MST paradigms. The results show that the median ECT stimulation strength in the brain is 3-11 times higher than that for MST, and that the stimulated brain volume is substantially higher with ECT (47-100%) than with MST (21%). Our study provides insight into the observed reduction of cognitive side effects in MST compared to ECT, and supports arguments for lowering ECT current amplitude as a means of curbing its side effects.

  10. TOWARD MORE REALISTIC ANALYTIC MODELS OF THE HELIOTAIL: INCORPORATING MAGNETIC FLATTENING VIA DISTORTION FLOWS

    Energy Technology Data Exchange (ETDEWEB)

    Kleimann, Jens; Fichtner, Horst [Ruhr-Universität Bochum, Fakultät für Physik und Astronomie, Institut für Theoretische Physik IV, Bochum (Germany); Röken, Christian [Universität Regensburg, Fakultät für Mathematik, Regensburg (Germany); Heerikhuisen, Jacob, E-mail: jk@tp4.rub.de, E-mail: hf@tp4.rub.de, E-mail: christian.roeken@mathematik.uni-regensburg.de, E-mail: jacob.heerikhuisen@uah.edu [Department of Space Science and Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

    2016-01-01

    Both physical arguments and simulations of the global heliosphere indicate that the tailward heliopause is flattened considerably in the direction perpendicular to both the incoming flow and the large-scale interstellar magnetic field. Despite this fact, all of the existing global analytical models of the outer heliosheath's magnetic field assume a circular cross section of the heliotail. To eliminate this inconsistency, we introduce a mathematical procedure by which any analytically or numerically given magnetic field can be deformed in such a way that the cross sections along the heliotail axis attain freely prescribed, spatially dependent values for their total area and aspect ratio. The distorting transformation of this method honors both the solenoidality condition and the stationary induction equation with respect to an accompanying flow field, provided that both constraints were already satisfied for the original magnetic and flow fields prior to the transformation. In order to obtain realistic values for the above parameters, we present the first quantitative analysis of the heliotail's overall distortion as seen in state-of-the-art three-dimensional hybrid MHD–kinetic simulations.

  11. Interaction between electromagnetic waves and energetic particles by a realistic density model

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Using a realistic density model,we present a first study on the interactions between electromagnetic waves and energetic particles in the inner magnetosphere.Numerical calculations show that as the latitude λ increases,the number density ne increases,and resonant frequency range moves to lower pitch angles.During L-mode/electron and L-mode/proton interactions,the pitch angle diffusion dominates over the momentum diffusion.This indicates that L-mode waves are primarily responsible for pitch angle scattering.For R-mode/electron interaction,the momentum diffusion is found to be comparable to the pitch angle diffusion,implying that R-mode waves can play an important role in both pitch angle scattering and stochastic acceleration of electrons.For R-mode/proton interaction,diffusion coefficients locate primarily below pitch angle 60° and increase as kinetic energy increases,suggesting that R-mode waves have potential for pitch angle scattering of highly energetic (~1 MeV) protons but cannot efficiently accelerate protons.

  12. Turbulent transport measurements in a cold model of GT-burner at realistic flow rates

    Directory of Open Access Journals (Sweden)

    Gobyzov Oleg

    2016-01-01

    Full Text Available In the present work simultaneous velocity field and passive admixture concentration field measurements at realistic flow-rates conditions in a non-reacting flow in a model of combustion chamber with an industrial mixing device are reported. In the experiments for safety reasons the real fuel (natural gas was replaced with neon gas to simulate stratification in a strongly swirling flow. Measurements were performed by means of planar laser-induced fluorescence (PLIF and particle image velocimetry technique (PIV at Reynolds number, based on the mean flow rate and nozzle diameter, ≈300 000. Details on experimental technique, features of the experimental setup, images and data preprocessing procedures and results of performed measurements are given in the paper. In addition to the raw velocity and admixture concentration data in-depth evaluation approaches aimed for estimation of turbulent kinetic energy (TKE components, assessment of turbulent Schmidt number and analysis of the gradient closure hypothesis from experimental data are presented in the paper.

  13. Computational approaches and metrics required for formulating biologically realistic nanomaterial pharmacokinetic models

    Science.gov (United States)

    Riviere, Jim E.; Scoglio, Caterina; Sahneh, Faryad D.; Monteiro-Riviere, Nancy A.

    2013-01-01

    The field of nanomaterial pharmacokinetics is in its infancy, with major advances largely restricted by a lack of biologically relevant metrics, fundamental differences between particles and small molecules of organic chemicals and drugs relative to biological processes involved in disposition, a scarcity of sufficiently rich and characterized in vivo data and a lack of computational approaches to integrating nanomaterial properties to biological endpoints. A central concept that links nanomaterial properties to biological disposition, in addition to their colloidal properties, is the tendency to form a biocorona which modulates biological interactions including cellular uptake and biodistribution. Pharmacokinetic models must take this crucial process into consideration to accurately predict in vivo disposition, especially when extrapolating from laboratory animals to humans since allometric principles may not be applicable. The dynamics of corona formation, which modulates biological interactions including cellular uptake and biodistribution, is thereby a crucial process involved in the rate and extent of biodisposition. The challenge will be to develop a quantitative metric that characterizes a nanoparticle's surface adsorption forces that are important for predicting biocorona dynamics. These types of integrative quantitative approaches discussed in this paper for the dynamics of corona formation must be developed before realistic engineered nanomaterial risk assessment can be accomplished.

  14. Underwriting information-theoretic accounts of quantum mechanics with a realist, psi-epistemic model

    Science.gov (United States)

    Stuckey, W. M.; Silberstein, Michael; McDevitt, Timothy

    2016-05-01

    We propose an adynamical interpretation of quantum theory called Relational Blockworld (RBW) where the fundamental ontological element is a 4D graphical amalgam of space, time and sources called a “spacetimesource element.” These are fundamental elements of space, time and sources, not source elements in space and time. The transition amplitude for a spacetimesource element is computed using a path integral with discrete graphical action. The action for a spacetimesource element is constructed from a difference matrix K and source vector J on the graph, as in lattice gauge theory. K is constructed from graphical field gradients so that it contains a non-trivial null space and J is then restricted to the row space of K, so that it is divergence-free and represents a conserved exchange of energy-momentum. This construct of K and J represents an adynamical global constraint between sources, the spacetime metric and the energy-momentum content of the spacetimesource element, rather than a dynamical law for time-evolved entities. To illustrate this interpretation, we explain the simple EPR-Bell and twin-slit experiments. This interpretation of quantum mechanics constitutes a realist, psi-epistemic model that might underwrite certain information-theoretic accounts of the quantum.

  15. Star Formation in Galaxy Mergers with Realistic Models of Stellar Feedback & the Interstellar Medium

    CERN Document Server

    Hopkins, Philip F; Hernquist, Lars; Narayanan, Desika; Hayward, Christopher C; Murray, Norman

    2012-01-01

    We use simulations with realistic models for stellar feedback to study galaxy mergers. These high resolution (1 pc) simulations follow formation and destruction of individual GMCs and star clusters. The final starburst is dominated by in situ star formation, fueled by gas which flows inwards due to global torques. The resulting high gas density results in rapid star formation. The gas is self gravitating, and forms massive (~10^10 M_sun) GMCs and subsequent super-starclusters (masses up to 10^8 M_sun). However, in contrast to some recent simulations, the bulk of new stars which eventually form the central bulge are not born in superclusters which then sink to the center of the galaxy, because feedback efficiently disperses GMCs after they turn several percent of their mass into stars. Most of the mass that reaches the nucleus does so in the form of gas. The Kennicutt-Schmidt law emerges naturally as a consequence of feedback balancing gravitational collapse, independent of the small-scale star formation micro...

  16. Numerical modeling of turbulent swirling flow in a multi-inlet vortex nanoprecipitation reactor using dynamic DDES

    Science.gov (United States)

    Hill, James C.; Liu, Zhenping; Fox, Rodney O.; Passalacqua, Alberto; Olsen, Michael G.

    2015-11-01

    The multi-inlet vortex reactor (MIVR) has been developed to provide a platform for rapid mixing in the application of flash nanoprecipitation (FNP) for manufacturing functional nanoparticles. Unfortunately, commonly used RANS methods are unable to accurately model this complex swirling flow. Large eddy simulations have also been problematic, as expensive fine grids to accurately model the flow are required. These dilemmas led to the strategy of applying a Delayed Detached Eddy Simulation (DDES) method to the vortex reactor. In the current work, the turbulent swirling flow inside a scaled-up MIVR has been investigated by using a dynamic DDES model. In the DDES model, the eddy viscosity has a form similar to the Smagorinsky sub-grid viscosity in LES and allows the implementation of a dynamic procedure to determine its coefficient. The complex recirculating back flow near the reactor center has been successfully captured by using this dynamic DDES model. Moreover, the simulation results are found to agree with experimental data for mean velocity and Reynolds stresses.

  17. Realistic modelling of observed seismic motion in compIex sedimentary basins

    Directory of Open Access Journals (Sweden)

    G. F. Panza

    1994-06-01

    Full Text Available Three applications of a numerical technique are illustrated to model realistically the seismic ground motion for complex two-dimensional structures. First we consider a sedimentary basin in the Friuli region, and we model strong motion records from an aftershock of the 1976 earthquake. Then we simulate the ground motion caused in Rome by the 1915, Fucino (Italy earthquake, and we compare our modelling with the damage distribution observed in the town. Finally we deal with the interpretation of ground motion recorded in Mexico City, as a consequence of earthquakes in the Mexican subduction zone. The synthetic signals explain the major characteristics (relative amplitudes, spectral amplification, frequency content of the considered seismograms, and the space distribution of the available macroseismic data. For the sedimentary basin in the Friuli area, parametric studies demonstrate the relevant sensitivity of the computed ground motion to small changes in the subsurface topography of the sedimentary basin, and in the velocity and quality factor of the sediments. The relative Arias Intensity, determined from our numerical simulation in Rome, is in very good agreoment with the distribution of damage observed during the Fucino earthquake. For epicentral distances in the range 50 km-100 km, the source location and not only the local soil conditions control the local effects. For Mexico City, the observed ground motion can be explained as resonance effects and as excitation of local surface waves, and the theoretical and the observed maximum spectral amplifications are very similar. In general, our numerical simulations estimate the maximum and average spectral amplification for specific sites, i.e. they are a very powerful tool for accurate micro-zonation

  18. Modeling the Performance Limitations and Prospects of Perovskite/Si Tandem Solar Cells under Realistic Operating Conditions.

    Science.gov (United States)

    Futscher, Moritz H; Ehrler, Bruno

    2017-09-08

    Perovskite/Si tandem solar cells have the potential to considerably out-perform conventional solar cells. Under standard test conditions, perovskite/Si tandem solar cells already outperform the Si single junction. Under realistic conditions, however, as we show, tandem solar cells made from current record cells are hardly more efficient than the Si cell alone. We model the performance of realistic perovskite/Si tandem solar cells under real-world climate conditions, by incorporating parasitic cell resistances, nonradiative recombination, and optical losses into the detailed-balance limit. We show quantitatively that when optimizing these parameters in the perovskite top cell, perovskite/Si tandem solar cells could reach efficiencies above 38% under realistic conditions, even while leaving the Si cell untouched. Despite the rapid efficiency increase of perovskite solar cells, our results emphasize the need for further material development, careful device design, and light management strategies, all necessary for highly efficient perovskite/Si tandem solar cells.

  19. Resolving Cognitive Conflict in a Realistic Situation with Modeling Characteristics: Coping with a Changing Reference in Fractions

    Science.gov (United States)

    Shahbari, Juhaina Awawdeh; Peled, Irit

    2015-01-01

    This study investigates the effect of using a realistic situation with modeling characteristics in creating and resolving a cognitive conflict to promote understanding of a changing reference in fraction calculations. The study was conducted among 96 seventh graders divided into 2 experimental groups and 1 control group. The experimental groups…

  20. Resolving Cognitive Conflict in a Realistic Situation with Modeling Characteristics: Coping with a Changing Reference in Fractions

    Science.gov (United States)

    Shahbari, Juhaina Awawdeh; Peled, Irit

    2015-01-01

    This study investigates the effect of using a realistic situation with modeling characteristics in creating and resolving a cognitive conflict to promote understanding of a changing reference in fraction calculations. The study was conducted among 96 seventh graders divided into 2 experimental groups and 1 control group. The experimental groups…

  1. Toward more realistic projections of soil carbon dynamics by Earth system models: SOIL CARBON MODELING

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Yiqi; Ahlstrom, Anders; Allison, Steven D.; Batjes, Niels H.; Brovkin, Victor; Carvalhais, N.; Chappell, Adrian; Ciais, Philippe; Davidson, Eric A.; Finzi, Adien; Georgiou, Katerina; Guenet, Bertrand; Hararuk, Oleksandra; Harden, Jennifer W.; He, Yujie; Hopkins, Francesca; Jiang, Lifen; Koven, C.; Jackson, Robert B.; Jones, Chris D.; Lara, Mark J.; Liang, Junyi; McGuire, A. David; Parton, William J.; Peng, Changhui; Randerson, J.; Salazar, Alejandro; Sierra , Carlos A.; Smith, Matthew J.; Tian, Hanqin; Todd-Brown, Katherine EO; Torn, Margaret S.; van Groenigen, Kees Jan; Wang, Ying Ping; West, Tristram O.; Wei, Yaxing; Wieder, William R.; Xia, Jianyang; Xu, Xia; Xu, Xiaofeng; Zhou, Tao

    2016-01-21

    Soil carbon (C) is a critical component of Earth system models (ESMs) and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the 3rd to 5th assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. Firstly, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by 1st-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic SOC dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Secondly, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based datasets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Thirdly, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable datasets are available to select the most representative model structure, constrain parameters, and

  2. How realistic are flat-ramp-flat fault kinematic models? Comparing mechanical and kinematic models

    Science.gov (United States)

    Cruz, L.; Nevitt, J. M.; Hilley, G. E.; Seixas, G.

    2015-12-01

    Rock within the upper crust appears to deform according to elasto-plastic constitutive rules, but structural geologists often employ kinematic descriptions that prescribe particle motions irrespective of these physical properties. In this contribution, we examine the range of constitutive properties that are approximately implied by kinematic models by comparing predicted deformations between mechanical and kinematic models for identical fault geometric configurations. Specifically, we use the ABAQUS finite-element package to model a fault-bend-fold geometry using an elasto-plastic constitutive rule (the elastic component is linear and the plastic failure occurs according to a Mohr-Coulomb failure criterion). We varied physical properties in the mechanical model (i.e., Young's modulus, Poisson ratio, cohesion yield strength, internal friction angle, sliding friction angle) to determine the impact of each on the observed deformations, which were then compared to predictions of kinematic models parameterized with identical geometries. We found that a limited sub-set of physical properties were required to produce deformations that were similar to those predicted by the kinematic models. Specifically, mechanical models with low cohesion are required to allow the kink at the bottom of the flat-ramp geometry to remain stationary over time. Additionally, deformations produced by steep ramp geometries (30 degrees) are difficult to reconcile between the two types of models, while lower slope gradients better conform to the geometric assumptions. These physical properties may fall within the range of those observed in laboratory experiments, suggesting that particle motions predicted by kinematic models may provide an approximate representation of those produced by a physically consistent model under some circumstances.

  3. Cortical sources of ERP in prosaccade and antisaccade eye movements using realistic source models

    Science.gov (United States)

    Richards, John E.

    2013-01-01

    The cortical sources of event-related-potentials (ERP) using realistic source models were examined in a prosaccade and antisaccade procedure. College-age participants were presented with a preparatory interval and a target that indicated the direction of the eye movement that was to be made. In some blocks a cue was given in the peripheral location where the target was to be presented and in other blocks no cue was given. In Experiment 1 the prosaccade and antisaccade trials were presented randomly within a block; in Experiment 2 procedures were compared in which either prosaccade and antisaccade trials were mixed in the same block, or trials were presented in separate blocks with only one type of eye movement. There was a central negative slow wave occurring prior to the target, a slow positive wave over the parietal scalp prior to the saccade, and a parietal spike potential immediately prior to saccade onset. Cortical source analysis of these ERP components showed a common set of sources in the ventral anterior cingulate and orbital frontal gyrus for the presaccadic positive slow wave and the spike potential. In Experiment 2 the same cued- and non-cued blocks were used, but prosaccade and antisaccade trials were presented in separate blocks. This resulted in a smaller difference in reaction time between prosaccade and antisaccade trials. Unlike the first experiment, the central negative slow wave was larger on antisaccade than on prosaccade trials, and this effect on the ERP component had its cortical source primarily in the parietal and mid-central cortical areas contralateral to the direction of the eye movement. These results suggest that blocked prosaccade and antisaccade trials results in preparatory or set effects that decreases reaction time, eliminates some cueing effects, and is based on contralateral parietal-central brain areas. PMID:23847476

  4. Valve morphology effect in aortic coarctation flow using realistic silicon models and magnetic resonance imaging

    Science.gov (United States)

    Marrufo, Oscar; Solis-Najera, Sergio; Pibarot, Philippe; Kadem, Lyes; Kesharvarz-Motamed, Zahra; Rodriguez, Alfredo O.; Garcia, Julio

    2014-11-01

    Aortic valve morphology and phenotype may alter the aortic wall structure and its normal flow hemodynamics. However, the relationship between altered flow patterns and progression of wall pathology is often not fully understood in patients with aortic coartation and needs larger experimental work. In this study, we introduced a compatible experimental setup with magnetic resonance imaging (MRI) using a realistic aortic coarctation (AoCo) silicon model which can replicate physiological flow conditions (pressure, flow-wave, and systemic load). We evaluated the aortic valve hemodynamics of a normal tricuspid valve and a stenotic bicuspid valve using valve effective orifice area (EOA), peak and mean transvalvular pressure gradient (TPG). AoCo severity was assessed by the AoCo pressure gradient. For the tricuspid valve we obtained an EOA = 1.89 cm2, a peak TPG = 10 mmHg, and a mean TPG = 5 mmHg. For the bicuspid valve we obtained an EOA = 1.03 cm2, a peak TPG = 37 mmHg and a mean TPG = 13 mmHg. Furthermore, AoCo with tricuspid valve led to a peak AoCo pressure gradient (PG) = 11 mmHg and a mean PG = 5 mmHg. AoCo with bicuspid valve led to a peak PG = 6 mmHg and a mean PG = 3 mmHg. Aortic flow reattachment was more evident in presence of bicuspid valve and helical flow was present in all cases. This study showed that silicon prototyping in combination with MRI velocity measurements could successfully be used to assess hemodynamic effects of aortic valve morphology in aortic coarctation flow.

  5. Cortical Sources of ERP in Prosaccade and Antisaccade Eye Movements using Realistic Source Models

    Directory of Open Access Journals (Sweden)

    John E Richards

    2013-07-01

    Full Text Available The cortical sources of event-related-potentials (ERP using realistic source models were examined in a prosaccade and antisaccade task. College-age participants were presented with a preparatory interval and a target that indicated the direction of the eye movement that was to be made. In some blocks a cue was given in the peripheral location where the target was to be presented and in other blocks no cue was given. In Experiment 1 the prosaccade and antisaccade trials were presented randomly within a block; in Experiment 2 procedures were compared in which either prosaccade and antisaccade trials were mixed in the same block, or trials were presented in separate blocks with only one type of eye movement. There was a central negative slow wave occurring prior to the target, a slow positive wave over the parietal scalp prior to the saccade, and a parietal spike potential immediately prior to saccade onset. Cortical source analysis of these ERP components showed a common set of sources in the ventral anterior cingulate and orbital frontal gyrus for the presaccadic positive slow wave and the spike potential. In Experiment 2 the same cued- and non-cued blocks were used, but prosaccade and antisaccade trials were presented in separate blocks. This resulted in a smaller difference in reaction time between prosaccade and antisaccade trials. Unlike the first experiment, the central negative slow wave was larger on antisaccade than on prosaccade trials, and this effect on the ERP component had its cortical source primarily in the parietal and mid-central cortical areas contralateral to the direction of the eye movement. These results suggest that blocked prosaccade and antisaccade trials results in preparatory or set effects that decreases reaction time, eliminates some cueing effects, and is based on contralateral parietal-central brain areas.

  6. Planar Inlet Design and Analysis Process (PINDAP)

    Science.gov (United States)

    Slater, John W.; Gruber, Christopher R.

    2005-01-01

    The Planar Inlet Design and Analysis Process (PINDAP) is a collection of software tools that allow the efficient aerodynamic design and analysis of planar (two-dimensional and axisymmetric) inlets. The aerodynamic analysis is performed using the Wind-US computational fluid dynamics (CFD) program. A major element in PINDAP is a Fortran 90 code named PINDAP that can establish the parametric design of the inlet and efficiently model the geometry and generate the grid for CFD analysis with design changes to those parameters. The use of PINDAP is demonstrated for subsonic, supersonic, and hypersonic inlets.

  7. Gas uptake in a three-generation model geometry with a flat inlet velocity during steady inspiration: comparison of axisymmetric and three-dimensional models.

    Science.gov (United States)

    Madasu, Srinath; Borhan, Ali; Ultman, James

    2007-05-01

    Mass transfer coefficients were predicted and compared for uptake of reactive gas system using an axisymmetric single-path model (ASPM) with experimentally predicted values in a two-generation geometry and with a three-dimensional computational fluid dynamics model (CFDM) in a three-generation model geometry at steady inspiratory flow with a flat inlet velocity profile. The flow and concentration fields in the ASPM were solved using Galerkin's finite element method and in the CFDM using a commercial finite element software FIDAP. ASPM predicted average gas phase mass transfer coefficients within 25% of the experimental values. Numerical results in terms of overall mass transfer coefficients from the two models within each bifurcation unit were compared for two different inlet flow rates, wall mass transfer coefficients, and bifurcation angles. The overall mass transfer coefficients variation with bifurcation unit from the ASPM and CFDM compared qualitatively and quantitatively closely at lower wall mass transfer coefficients for both 40 degree and 70 degree bifurcation angles. But at higher wall mass transfer coefficients, quantitatively they were off in the range of 2-10% for 40 degree bifurcation angle and in the range of 4-15% for 70 degree bifurcation angle. Both CFDM and ASPM predict the same trends of increase in mass transfer coefficients with inlet flow, wall mass transfer coefficients, and during inspiration compared to expiration. Higher mass transfer coefficients were obtained with a flat velocity profile compared to a parabolic velocity profile using ASPM. These results validate the simplified ASPM and the complex CFDM.

  8. Numerical simulation of wave propagation in a realistic model of the human external ear.

    Science.gov (United States)

    Fadaei, Mohaddeseh; Abouali, Omid; Emdad, Homayoun; Faramarzi, Mohammad; Ahmadi, Goodarz

    2015-01-01

    In this study, a numerical investigation is performed to evaluate the effects of high-pressure sinusoidal and blast wave's propagation around and inside of a human external ear. A series of computed tomography images are used to reconstruct a realistic three-dimensional (3D) model of a human ear canal and the auricle. The airflow field is then computed by solving the governing differential equations in the time domain using a computational fluid dynamics software. An unsteady algorithm is used to obtain the high-pressure wave propagation throughout the ear canal which is validated against the available analytical and numerical data in literature. The effects of frequency, wave shape, and the auricle on pressure distribution are then evaluated and discussed. The results clearly indicate that the frequency plays a key role on pressure distribution within the ear canal. At 4 kHz frequency, the pressure magnitude is much more amplified within the ear canal than the frequencies of 2 and 6 kHz, for the incident wave angle of 90° investigated in this study, attributable to the '4-kHz notch' in patients with noise-induced hearing loss. According to the results, the pressure distribution patterns at the ear canal are very similar for both sinusoidal pressure waveform with the frequency of 2 kHz and blast wave. The ratio of the peak pressure value at the eardrum to that at the canal entrance increases from about 8% to 30% as the peak pressure value of the blast wave increases from 5 to 100 kPa for the incident wave angle of 90° investigated in this study. Furthermore, incorporation of the auricle to the ear canal model is associated with centerline pressure magnitudes of about 50% and 7% more than those of the ear canal model without the auricle throughout the ear canal for sinusoidal and blast waves, respectively, without any significant effect on pressure distribution pattern along the ear canal for the incident wave angle of 90° investigated in this study.

  9. Formation and stability of ridge-ridge-ridge triple junctions in rheologically realistic lithosphere model

    Science.gov (United States)

    Gerya, Taras; Burov, Evgueni

    2015-04-01

    -branch junction formation and evolution by using high-resolution 3D numerical mechanical experiments that take into account realistic thermo-rheological structure and rheology of the lithosphere. We find that two major types of quadruple and triple junctions are formed under bi-directional or multidirectional far-field stress field: (i) plate rifting junctions are formed by the initial plate fragmentation and can be subsequently re-arranged into (ii) oceanic spreading junctions controlled by the new oceanic crust accretion. In particular, we document initial formation and destabilization of quadruple R-R-R-R junctions as initial plate rifting structures under bi-directional extension. In most cases, quadruple plate rifting junctions rapidly (typically within 1-2 Myr) evolve towards formation of two diverging triple oceanic spreading junctions connected by a linear spreading center lengthening with time. This configuration remains stable over long time scales. However, under certain conditions, quadruple junctions may also remain relatively stable. Asymmetric stretching results in various configurations, for example formation of "T-junctions" with trans-extensional components and combination of fast and slow spreading ridges. Combined with plume impingement, this scenario evolves in realistic patterns closely resembling observed plate dynamics. In particular, opening of the Red Sea and of the Afar rift system find a logical explanation within a single model. Numerical experiments also suggest that several existing oceanic spreading junctions form as the result of plate motions rearrangements after which only one of two plates spreading along the ridge become subjected to bi-directional spreading.

  10. Influence of skull anisotropy for the forward and inverse problem in EEG: simulation studies using FEM on realistic head models.

    Science.gov (United States)

    Marin, G; Guerin, C; Baillet, S; Garnero, L; Meunier, G

    1998-01-01

    For the sake of realism in the description of conduction from primary neural currents to scalp potentials, we investigated the influence of skull anisotropy on the forward and inverse problems in brain functional imaging with EEG. At present, all methods available for cortical imaging assume a spherical geometry, or when using realistic head shapes do not consider the anisotropy of head tissues. However, to our knowledge, no study relates the implication of this simplifying hypothesis on the spatial resolution of EEG for source imaging. In this paper, a method using finite elements in a realistic head geometry is implemented and validated. The influence of erroneous conductivity values for the head tissues is presented, and results show that the conductivities of the brain and the skull in the radial orientation are the most critical ones. In the inverse problem, this influence has been evaluated with simulations using a distributed source model with a comparison of two regularization techniques, with the isotropic model working on data sets produced by a nonisotropic model. Regularization with minimum norm priors produces source images with spurious activity, meaning that the errors in the head model totally annihilate any localization ability. But nonlinear regularization allows the accurate recovery of simultaneous spots of activity, while the restoration of very close active regions is profoundly disabled by errors in the head model. We conclude that for robust cortical source imaging with EEG, a realistic head model taking anisotropy of tissues into account should be used.

  11. Influences of flow loss and inlet distortions from radial inlets on the performances of centrifugal compressor stages

    Energy Technology Data Exchange (ETDEWEB)

    Han, Feng Hui; Mao, Yi Jun [School of Energy and Power Engineering, Xi' an Jiaotong University, Xi' an (China); Tan, Ji Jian [Dept. of Research and Development, Shenyang Blower Works Group Co., Ltd., Shenyang (China)

    2016-11-15

    Radial inlets are typical upstream components of multistage centrifugal compressors. Unlike axial inlets, radial inlets generate additional flow loss and introduce flow distortions at impeller inlets. Such distortions negatively affect the aerodynamic performance of compressor stages. In this study, industrial centrifugal compressor stages with different radial inlets are investigated via numerical simulations. Two reference models were built, simulated, and compared with each original compressor stage to analyze the respective and coupling influences of flow loss and inlet distortions caused by radial inlets on the performances of the compressor stage and downstream components. Flow loss and inlet distortions are validated as the main factors through which radial inlets negatively affect compressor performance. Results indicate that flow loss inside radial inlets decreases the performance of the whole compressor stage but exerts minimal effect on downstream components. By contrast, inlet distortions induced by radial inlets negatively influence the performance of the whole compressor stage and exert significant effects on downstream components. Therefore, when optimizing radial inlets, the reduction of inlet distortions might be more effective than the reduction of flow loss. This research provides references and suggestions for the design and improvement of radial inlets.

  12. A Non-Equilibrium Sediment Transport Model for Coastal Inlets and Navigation Channels

    Science.gov (United States)

    2011-01-01

    Navigation Channels Alejandro Sánchez† and Weiming Wu‡ ABSTRACT SANCHEZ, A. and WU, W., 2011. A Non-Equilibrium Sediment Transport Model...2009; accessed January 20, 2009). Nicholson, J.; Brøker, I.; Roelvink, J. A.; Price, D.; Tanguy, J. M., and Moreno , L., 1997. Intercomparison of

  13. INLET STRATIFICATION DEVICE

    DEFF Research Database (Denmark)

    2006-01-01

    An inlet stratification device (5) for a circuit circulating a fluid through a tank (1 ) and for providing and maintaining stratification of the fluid in the tank (1 ). The stratification de- vice (5) is arranged vertically in the tank (1) and comprises an inlet pipe (6) being at least partially...... formed of a flexible porous material and having an inlet (19) and outlets formed of the pores of the porous material. The stratification device (5) further comprises at least one outer pipe (7) surrounding the inlet pipe (6) in spaced relationship thereto and being at least partially formed of a porous...

  14. Impact of Hurricanes and Nor'easters on a Migrating Inlet System

    Science.gov (United States)

    Hopkins, J.; Elgar, S.; Raubenheimer, B.

    2016-12-01

    After breaching in 2007, Katama Inlet, connecting Katama Bay to the Atlantic Ocean on the south shore of Martha's Vineyard, MA, migrated 2 km until it closed in 2015. Bathymetric surveys before and after Hurricanes Irene (2011) and Sandy (2012) indicate the strong waves and currents associated with these storms caused 2 m of erosion and deposition around the inlet mouth. The waves, currents, and bathymetric change observed during the hurricanes were used to validate the hydrodynamic and morphodynamic components of a Delft3D numerical model of the Martha's Vineyard coastline for storm (> 3 m wave heights) conditions. When driven with observed bathymetry and offshore waves, as well as simulated (WaveWatch3) winds and barometric pressures, the model reproduces the pattern and range of bathymetric change observed around the inlet. Model simulations of realistic (i.e., Irene and Sandy) and idealized storm conditions with a range of durations and wave conditions are used to test the relative importance of short-duration, high-intensity storms (hurricanes) and longer-duration, lower-intensity storms (nor'easters) on inlet migration. The simulations suggest that longer-duration, lower-intensity storms cause a higher range and variance in bathymetric change around the inlet than shorter-duration, higher-intensity storms. However, the simulations also suggest that the storm-induced migration of the inlet depends more on the wave direction at the peak of the storm than on the duration of the storm peak. The effect of storms on inlet migration over yearly time scales will be discussed. Funded by NSF, NOAA, ONR, and ASD(R&E).

  15. Realistic modelling of the seismic input Site effects and parametric studies

    CERN Document Server

    Romanelli, F; Vaccari, F

    2002-01-01

    We illustrate the work done in the framework of a large international cooperation, showing the very recent numerical experiments carried out within the framework of the EC project 'Advanced methods for assessing the seismic vulnerability of existing motorway bridges' (VAB) to assess the importance of non-synchronous seismic excitation of long structures. The definition of the seismic input at the Warth bridge site, i.e. the determination of the seismic ground motion due to an earthquake with a given magnitude and epicentral distance from the site, has been done following a theoretical approach. In order to perform an accurate and realistic estimate of site effects and of differential motion it is necessary to make a parametric study that takes into account the complex combination of the source and propagation parameters, in realistic geological structures. The computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different sources and stru...

  16. Sensor and actuator modeling of a realistic wheeled mobile robot simulator

    OpenAIRE

    José Gonçalves; José Lima; Hélder Filipe Pinto de Oliveira; Paulo José Cerqueira Gomes da Costa

    2008-01-01

    This paper describes the sensor and actuator modelingof a realistic wheeled mobile robot simulator. The motivationof developing such simulator is to produce a personalizedversatile tool that allows production and validationof robot software reducing considerably the developmenttime. The mobile robot simulator was developed in ObjectPascal with its dynamics based on the ODE (OpenDynamics Engine), allowing to develop robot software fora three wheel omnidirectional robot equipped with Infra-Red ...

  17. Modelling of laminar flow in the inlet section of rectangular microchannels

    Science.gov (United States)

    Martinelli, Matteo; Viktorov, Vladimir

    2009-02-01

    This paper is a study of laminar flow in rectangular microchannels. The behaviour of compressible and incompressible fluids in microchannels was simulated using CFD software. Numerical data were compared to experimental measurements to test the validity of CFD models. The velocity profile of flow developing inside the channel is described as a function of the Reynolds number Re, varying from 100 to 2000, and the aspect ratio h/w, ranging from 1 to 0.125. The fundamental importance of the entrance length of microchannels is highlighted. Numerical data were applied to define analytical formulae covering the minimum entrance length for fully developed laminar flow of compressible fluids, viscous stress and incremental pressure drop effect during flow development, and the velocity profiles of flow for compressible and incompressible fluids.

  18. Atmospheric response to a realistic coastal polynya in Terra Nova Bay (Antarctica) simulated by ETA model.

    Science.gov (United States)

    Morelli, S.; Casini, G.; Parmiggiani, F.

    2009-04-01

    Coastal polynyas are areas of open water (and/or very thin ice) which form adjacent to coasts or blocking feature in polar regions during the wintertime, when the sea water is expected to be ice covered. They are thought to be maintained by strong offshore winds blowing over these area and/or by ocean currents. Sea ice is removed as it forms and drifted offshore. In polynya areas a direct contact is established between the relatively warm sea water and the cold, dry atmosphere. As a consequence, the physical characteristics of the atmospheric boundary layer change. The work presented here concerns a real polynya event in the region of Terra Nova Bay (TNB), Antarctica, where a recurring coastal polynya occurs nearby the Italian Antarctic Base. The aim is the study of atmospheric response to the presence of a open water area of realistic size by three-dimensional numerical simulations. Atmospheric numerical modelling is a fundamental tool for the study of air - polynya interactions in the remote polar regions, where observational data are difficult. The numerical model used for the simulations is a recent version of ETA model (Mesinger et al., 2006), with the addition of a piecewise linear advection for the wind field. ECMWF and NCEP data provided the initial and boundary conditions. A previous version of the model had already been successfully used in the Antarctic area (De Carolis et al, 2006, Casini and Morelli, 2007). As a first step to analyze the polynya event, numerical simulation was performed for the period from 12 to 17 July 2006 in order to study the development of the katabatic wind (Morelli and Casini, 2008; Morelli, 2008). Daily satellite images, concerning the period, display that a sea ice free area formed on 15 and 16 July, reaching its maximum extension of about 4000 km2 on 16 July (Morelli et al.,2007). In order to gain insight on the atmospheric response to open water area within a sea ice field, ETA model runs were carried out from 15 to 17 July

  19. EXPERIMENTAL STUDIES ON SWIRLING AND RECIRCULATING TWO-PHASE FLOW FIELD IN A COLD MODEL OF DUAL-INLET SUDDEN-EXPANSION COMBUSTOR

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The axial and tangential velocities of gas and particle phases and particle concentration for turbulent swirling and recirculating gas-particle (simulating gas-droplet) flows in a cold model of a dual-inlet sudden-expansion combustor with partially tangential central tubes, proposed by the present authors, were measured by using a 2-D LDV system and a laser optic fiber system combined with a sampling probe. The results show that there are both gas and particle strongly reverse flows and swirling flows in the head part of the combustor. The velocity slip between gas and particle phases is remarkable. The particle concentration is higher near the wall and lower near the axis. There are two peaks in the concentration profiles near the inlet tubes. The above-obtained flow characteristics are favorable to ignition, flame stabilization and combustion. The results can also be used to validate the numerical modeling.

  20. Do dental undergraduates think that Thiel-embalmed cadavers are a more realistic model for teaching exodontia?

    Science.gov (United States)

    Hanson, C; Wilkinson, T; Macluskey, M

    2016-12-20

    Teaching exodontia to novice undergraduates requires a realistic model. Thiel-embalmed cadavers retain the flexibility of the soft tissues and could be used to teach exodontia. The objective was to determine whether Thiel-embalmed cadavers were perceived to be a more realistic model by undergraduates in comparison with mannequins. Over a period of 4 years (2011-2014), students were randomly assigned into two groups: those taught exodontia on mannequins only (NT) and those who also experienced cadaveric teaching (T). This was followed by an assessment. There were 174 students in the T group and 108 in the NT group. Sixty-five per cent of the T group and 69% of the NT group provided feedback. Ninety-eight per cent (98%) felt that they had been advantaged by being included in the group compared with 95% in the NT who felt disadvantaged. The majority (98%) thought that using the cadavers was advantageous and gave a realistic feel for soft tissue management (89%) and that it was similar to managing a patient (81%). Self-reported confidence in undertaking an extraction was not different between the two groups (P=.078), and performance in the extraction assessment was not significantly different between the two groups over the 4 years (P=.8). The Thiel-embalmed cadavers were well received by the students who found it a more realistic model for exodontia than a mannequin, even though this did not impact on their performance in a following assessment. Future work on these cadavers may be expanded to include surgical procedures. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  1. Inlet stratification device

    DEFF Research Database (Denmark)

    2014-01-01

    ) with an inlet passage way (16). The upper end of the inlet pipe (6) is connected with a top cap (9). The top cap (9) and the bottom cap (10) are mutually connected by means of a wire (8) and the top cap (9) is configured as a floating device providing a buoyancy force larger than the downwardly directed force......An inlet stratification (5) is adapted to be arranged vertically in a tank (1) during operation. The stratification device (5) comprises an inlet pipe (6) formed of a flexible porous material and having a lower and upper end. The lower end of the inlet pipe (6) is connected to a bottom cap (10...

  2. Wounded nucleon model with realistic nucleon-nucleon collision profile and observables in relativistic heavy-ion collisions

    CERN Document Server

    Rybczyński, Maciej

    2011-01-01

    We investigate the influence of the nucleon-nucleon collision profile (probability of interaction as a function of the nucleon-nucleon impact parameter) in the wounded nucleon model and its extensions on several observables measured in relativistic heavy-ion collisions. We find that the participant eccentricity coefficient, $\\epsilon^\\ast$, as well as the higher harmonic coefficients, $\\epsilon_n^\\ast$, are reduced by 10-20% for mid-peripheral collisions when the realistic (Gaussian) profile is used, as compared to the case with the commonly-used hard-sphere profile. Similarly, the multiplicity fluctuations, treated as the function of the number of wounded nucleons in one of the colliding nuclei, are reduced by 10-20%. This demonstrates that the Glauber Monte Carlo codes should necessarily use the realistic nucleon-nucleon collision profile in precision studies of these observables. The Gaussian collision profile is built-in in {\\tt GLISSANDO}.

  3. Transient analysis of single stage GM type double inlet pulse tube cryocooler

    Science.gov (United States)

    Gujarati, P. B.; Desai, K. P.; Naik, H. B.; Atrey, M. D.

    2015-12-01

    Transient analysis of single stage GM type double inlet pulse tube cryocooler is carried out using a one dimensional numerical model based on real gas properties of helium. The model solves continuity, momentum and energy equation for gas and solid to analyse the physical process occurring inside of the pulse tube cryocooler. Finite volume method is applied to discretize the governing equations with realistic initial and boundary conditions. Input data required for solving the model are the design data and operating parameters viz. pressure waveform from the compressor, regenerator matrix data, and system geometry including pulse tube, regenerator size and operating frequency for pulse tube cryocooler. The model investigates the effect of orifice opening, double inlet opening, pressure ratio, system geometry on no load temperature and refrigeration power at various temperatures for different charging pressure. The results are compared with experimental data and reasonable agreement is observed. The model can further be extended for designing two stage pulse tube cryocooler.

  4. Seasonal dynamics of adjoining tidal coastal inlet on east coast of India ­measurements and modelling

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, S.; Reddy, N.A.; Ramanamurty, M.V.; ManiMurali, R.; ArunaKumar, A.; Rao, S.

    The opening and closure of coastal tidal inlets play a major role in regulating the water and sediment exchange between the river and ocean as well as in the interruption of the longshore sediment transport. The present work is an effort...

  5. Can hyper-realistic physical models of peripheral vessel exposure and fasciotomy replace cadavers for performance assessment?

    Science.gov (United States)

    Holzmacher, Jeremy; Sarani, Babak; Puche, Adam; Granite, Guinevere; Shalin, Valerie; Pugh, Kristy; Teeter, William; Tisherman, Samuel; Shackelford, Stacy; Mackenzie, Colin F

    2017-07-01

    Work-hour restrictions have reduced operative experience for residents. The Advanced Surgical Skills for Exposure in Trauma (ASSET) course fills this training gap. Cadaver use has limitations including cost and availability. Hyper-realistic synthetic models may provide an alternative to cadavers. We compared same surgeon performance between synthetic and cadaveric models to determine interchangeability for formative evaluation. Forty residents (realistic of all procedures. Faculty did significantly better on the synthetic model in all procedures. All participants completed procedures nearly twice as quickly (5.61 ± 3.21 vs. 10.08 ± 4.66 minutes) and performed fewer errors on the synthetic model (113 vs. 53, p < 0.01; 118 vs. 76, p = 0.03, respectively). Same surgeons performed procedures quicker and with fewer errors on the synthetic model. Residents performed similarly on both model types, this likely represents the unfamiliarity neophytes bring to new procedures. This suggests that the synthetic model, with easily discernible and standardized anatomy, may be useful in the early stages of training to understand critical procedural steps. The difficulty of the cadaver is more apt to assess and evaluate the experienced surgeon and identify opportunities for improvement. Prognostic, level III.

  6. A realistic neural mass model of the cortex with laminar-specific connections and synaptic plasticity - evaluation with auditory habituation.

    Directory of Open Access Journals (Sweden)

    Peng Wang

    Full Text Available In this work we propose a biologically realistic local cortical circuit model (LCCM, based on neural masses, that incorporates important aspects of the functional organization of the brain that have not been covered by previous models: (1 activity dependent plasticity of excitatory synaptic couplings via depleting and recycling of neurotransmitters and (2 realistic inter-laminar dynamics via laminar-specific distribution of and connections between neural populations. The potential of the LCCM was demonstrated by accounting for the process of auditory habituation. The model parameters were specified using Bayesian inference. It was found that: (1 besides the major serial excitatory information pathway (layer 4 to layer 2/3 to layer 5/6, there exists a parallel "short-cut" pathway (layer 4 to layer 5/6, (2 the excitatory signal flow from the pyramidal cells to the inhibitory interneurons seems to be more intra-laminar while, in contrast, the inhibitory signal flow from inhibitory interneurons to the pyramidal cells seems to be both intra- and inter-laminar, and (3 the habituation rates of the connections are unsymmetrical: forward connections (from layer 4 to layer 2/3 are more strongly habituated than backward connections (from Layer 5/6 to layer 4. Our evaluation demonstrates that the novel features of the LCCM are of crucial importance for mechanistic explanations of brain function. The incorporation of these features into a mass model makes them applicable to modeling based on macroscopic data (like EEG or MEG, which are usually available in human experiments. Our LCCM is therefore a valuable building block for future realistic models of human cognitive function.

  7. Implementation of position assimilation for ARGO floats in a realistic Mediterranean Sea OPA model and twin experiment testing

    Directory of Open Access Journals (Sweden)

    V. Taillandier

    2006-05-01

    Full Text Available In this paper, a Lagrangian assimilation method is presented and implemented in a realistic OPA OGCM with the goal of providing an assessment of the assimilation of realistic Argo float position data. We focus on an application in the Mediterranean Sea, where in the framework of the MFSTEP project an array of Argo floats have been deployed with parking depth at 350 m and sampling interval of 5 days. In order to quantitatively test the method, the ''twin experiment'' approach is followed and synthetic trajectories are considered. The method is first tested using ''perfect'' data, i.e. without shear drift errors and with relatively high coverage. Results show that the assimilation is effective, correcting the velocity field at the parking depth, as well as the velocity profiles and the geostrophically adjusted mass field. We then consider the impact of realistic datasets, which are spatially sparse and characterized by shear drift errors. Such data provide a limited global correction of the model state, but they efficiently act on the location, intensity and shape of the described mesoscale structures of the intermediate circulation.

  8. A real-time photo-realistic rendering algorithm of ocean color based on bio-optical model

    Science.gov (United States)

    Ma, Chunyong; Xu, Shu; Wang, Hongsong; Tian, Fenglin; Chen, Ge

    2016-12-01

    A real-time photo-realistic rendering algorithm of ocean color is introduced in the paper, which considers the impact of ocean bio-optical model. The ocean bio-optical model mainly involves the phytoplankton, colored dissolved organic material (CDOM), inorganic suspended particle, etc., which have different contributions to absorption and scattering of light. We decompose the emergent light of the ocean surface into the reflected light from the sun and the sky, and the subsurface scattering light. We establish an ocean surface transmission model based on ocean bidirectional reflectance distribution function (BRDF) and the Fresnel law, and this model's outputs would be the incident light parameters of subsurface scattering. Using ocean subsurface scattering algorithm combined with bio-optical model, we compute the scattering light emergent radiation in different directions. Then, we blend the reflection of sunlight and sky light to implement the real-time ocean color rendering in graphics processing unit (GPU). Finally, we use two kinds of radiance reflectance calculated by Hydrolight radiative transfer model and our algorithm to validate the physical reality of our method, and the results show that our algorithm can achieve real-time highly realistic ocean color scenes.

  9. Realistic modelling of the effects of asynchronous motion at the base of bridge piers

    CERN Document Server

    Romanelli, F; Vaccari, F

    2002-01-01

    Frequently long-span bridges provide deep valley crossings, which require special consideration due to the possibility of local amplification of the ground motion as a consequence of topographical irregularities and local soil conditions. This does in fact cause locally enhanced seismic input with the possibility for the bridge piers to respond asynchronously. This introduces special design requirements so that possible out-of-phase ground displacements and the associated large relative displacements of adjacent piers can be accommodated without excessive damage. Assessment of the local variability of the ground motion due to local lateral heterogeneities and to attenuation properties is thus crucial toward the realistic definition of the asynchronous motion at the base of the bridge piers. We illustrate the work done in the framework of a large international cooperation to assess the importance of non-synchronous seismic excitation of long structures. To accomplish this task we compute complete synthetic acc...

  10. FDTD Analysis of ELF Wave Propagation for Realistic Subionospheric Waveguide Models

    Science.gov (United States)

    Otsuyama, Takuya; Hayakawa, Masashi

    The space formed by the ground and ionosphere is known to act as a resonator for extremely low frequency (ELF) waves. Lightning discharges trigger this global resonance, which is known as Schumann resonance. Even though the inhomogeneity (like day-night asymmetry, local perturbation etc.) is important for such a subionospheric ELF propagation, the previous analyses have been always made by some approximations because the problem is too complicated to be analyzed by any exact full-wave analysis. This paper presents the application of the conventional numerical FDTD (finite difference time domain) method to such a subionospheric ELF wave propagation, in which any kinds of inhomogeneities can be included in this analysis. The present paper is intended to demonstrate the workability of this method for a realistic waveguide (with day-night asymmetry), by comparing the results from this method with those by the corresponding analytical method.

  11. A Real-Time Photo-Realistic Rendering Algorithm of Ocean Color Based on Bio-Optical Model

    Institute of Scientific and Technical Information of China (English)

    MA Chunyong; XU Shu; WANG Hongsong; TIAN Fenglin; CHEN Ge

    2016-01-01

    A real-time photo-realistic rendering algorithm of ocean color is introduced in the paper, which considers the impact of ocean bio-optical model. The ocean bio-optical model mainly involves the phytoplankton, colored dissolved organic material (CDOM), inorganic suspended particle,etc., which have different contributions to absorption and scattering of light. We decompose the emergent light of the ocean surface into the reflected light from the sun and the sky, and the subsurface scattering light. We estab-lish an ocean surface transmission model based on ocean bidirectional reflectance distribution function (BRDF) and the Fresnel law, and this model’s outputs would be the incident light parameters of subsurface scattering. Using ocean subsurface scattering algorithm combined with bio-optical model, we compute the scattering light emergent radiation in different directions. Then, we blend the re-flection of sunlight and sky light to implement the real-time ocean color rendering in graphics processing unit (GPU). Finally, we use two kinds of radiance reflectance calculated by Hydrolight radiative transfer model and our algorithm to validate the physical reality of our method, and the results show that our algorithm can achieve real-time highly realistic ocean color scenes.

  12. Optimized methods for epilepsy therapy development using an etiologically realistic model of focal epilepsy in the rat.

    Science.gov (United States)

    Eastman, Clifford L; Fender, Jason S; Temkin, Nancy R; D'Ambrosio, Raimondo

    2015-02-01

    Conventionally developed antiseizure drugs fail to control epileptic seizures in about 30% of patients, and no treatment prevents epilepsy. New etiologically realistic, syndrome-specific epilepsy models are expected to identify better treatments by capturing currently unknown ictogenic and epileptogenic mechanisms that operate in the corresponding patient populations. Additionally, the use of electrocorticography permits better monitoring of epileptogenesis and the full spectrum of acquired seizures, including focal nonconvulsive seizures that are typically difficult to treat in humans. Thus, the combined use of etiologically realistic models and electrocorticography may improve our understanding of the genesis and progression of epilepsy, and facilitate discovery and translation of novel treatments. However, this approach is labor intensive and must be optimized. To this end, we used an etiologically realistic rat model of posttraumatic epilepsy, in which the initiating fluid percussion injury closely replicates contusive closed-head injury in humans, and has been adapted to maximize epileptogenesis and focal non-convulsive seizures. We obtained week-long 5-electrode electrocorticography 1 month post-injury, and used a Monte-Carlo-based non-parametric bootstrap strategy to test the impact of electrode montage design, duration-based seizure definitions, group size and duration of recordings on the assessment of posttraumatic epilepsy, and on statistical power to detect antiseizure and antiepileptogenic treatment effects. We found that use of seizure definition based on clinical criteria rather than event duration, and of recording montages closely sampling the activity of epileptic foci, maximize the power to detect treatment effects. Detection of treatment effects was marginally improved by prolonged recording, and 24h recording epochs were sufficient to provide 80% power to detect clinically interesting seizure control or prevention of seizures with small groups

  13. EXPERIMENTAL STUDIES ON SWIRLING ANDRECIRCULATING TWO-PHASE FLOW FIELD IN A COLD MODEL OF DUAL-INLET SUDDEN-EXPANSION COMBUSTOR

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The dual-inlet liquid-spray-fuelled sudden-expansion combustors are frequently adopted in ramjet engines. The original combustors with swirlers in the inlet tubes frequently suffer from poor ignition, low flame stabilization and poor combustion performance due to insufficient sizes of recirculation zones in the head part of the combustor. There are only very small recirculation zones behind the swirlers. To improve the performance of the combustors, a new configuration is proposed by the authors, in which a small central tube instead of the original swirler is mounted in the inlet tube of the combustor with a tangential angle for creating swirling flows and enlarging the recirculation zones. So, it is expected to know the gas-droplet flow behavior after mounting the central tube. The turbulent swirling and recirculating gas-droplet flows in a dual-inlet sudden-expansion combustor are very complex. In the head part of the combustor there are recirculating flows. In the whole combustor there are swirling flows with a Rankine-vortex structure (solid-body rotation plus free vortex) of tangential velocity profiles. There should be obvious velocity slip between the gas and droplet phases due to the differences in inertia and centrifugal forces. The recirculating and swirling gas-particle flows were previously measured using LDV or PDPA[1~3]. In this paper the experimental studies on two-phase flows were carried out in a cold model of the combustor, and the motion of solid particles is used to simulate that of liquid droplets. The gas and particle (simulating the droplets) velocities were measured using a 2-D LDV system and the particle (simulating the droplet) concentration distribution is measured using a laser optic fiber system and a sampling probe. The purpose of this experimental study is not to simulate the real combustion regime, but to understand the features of the improved two-phase flow field using a central tube in the inlet tube and to provide the data

  14. Bayesian Modal Estimation of the Four-Parameter Item Response Model in Real, Realistic, and Idealized Data Sets.

    Science.gov (United States)

    Waller, Niels G; Feuerstahler, Leah

    2017-03-17

    In this study, we explored item and person parameter recovery of the four-parameter model (4PM) in over 24,000 real, realistic, and idealized data sets. In the first analyses, we fit the 4PM and three alternative models to data from three Minnesota Multiphasic Personality Inventory-Adolescent form factor scales using Bayesian modal estimation (BME). Our results indicated that the 4PM fits these scales better than simpler item Response Theory (IRT) models. Next, using the parameter estimates from these real data analyses, we estimated 4PM item parameters in 6,000 realistic data sets to establish minimum sample size requirements for accurate item and person parameter recovery. Using a factorial design that crossed discrete levels of item parameters, sample size, and test length, we also fit the 4PM to an additional 18,000 idealized data sets to extend our parameter recovery findings. Our combined results demonstrated that 4PM item parameters and parameter functions (e.g., item response functions) can be accurately estimated using BME in moderate to large samples (N ⩾ 5, 000) and person parameters can be accurately estimated in smaller samples (N ⩾ 1, 000). In the supplemental files, we report annotated [Formula: see text] code that shows how to estimate 4PM item and person parameters in [Formula: see text] (Chalmers, 2012 ).

  15. Credit Card Fraud Detection: A Realistic Modeling and a Novel Learning Strategy.

    Science.gov (United States)

    Dal Pozzolo, Andrea; Boracchi, Giacomo; Caelen, Olivier; Alippi, Cesare; Bontempi, Gianluca

    2017-09-14

    Detecting frauds in credit card transactions is perhaps one of the best testbeds for computational intelligence algorithms. In fact, this problem involves a number of relevant challenges, namely: concept drift (customers' habits evolve and fraudsters change their strategies over time), class imbalance (genuine transactions far outnumber frauds), and verification latency (only a small set of transactions are timely checked by investigators). However, the vast majority of learning algorithms that have been proposed for fraud detection rely on assumptions that hardly hold in a real-world fraud-detection system (FDS). This lack of realism concerns two main aspects: 1) the way and timing with which supervised information is provided and 2) the measures used to assess fraud-detection performance. This paper has three major contributions. First, we propose, with the help of our industrial partner, a formalization of the fraud-detection problem that realistically describes the operating conditions of FDSs that everyday analyze massive streams of credit card transactions. We also illustrate the most appropriate performance measures to be used for fraud-detection purposes. Second, we design and assess a novel learning strategy that effectively addresses class imbalance, concept drift, and verification latency. Third, in our experiments, we demonstrate the impact of class unbalance and concept drift in a real-world data stream containing more than 75 million transactions, authorized over a time window of three years.

  16. Larval dispersal modeling of pearl oyster Pinctada margaritifera following realistic environmental and biological forcing in Ahe atoll lagoon.

    Directory of Open Access Journals (Sweden)

    Yoann Thomas

    Full Text Available Studying the larval dispersal of bottom-dwelling species is necessary to understand their population dynamics and optimize their management. The black-lip pearl oyster (Pinctada margaritifera is cultured extensively to produce black pearls, especially in French Polynesia's atoll lagoons. This aquaculture relies on spat collection, a process that can be optimized by understanding which factors influence larval dispersal. Here, we investigate the sensitivity of P. margaritifera larval dispersal kernel to both physical and biological factors in the lagoon of Ahe atoll. Specifically, using a validated 3D larval dispersal model, the variability of lagoon-scale connectivity is investigated against wind forcing, depth and location of larval release, destination location, vertical swimming behavior and pelagic larval duration (PLD factors. The potential connectivity was spatially weighted according to both the natural and cultivated broodstock densities to provide a realistic view of connectivity. We found that the mean pattern of potential connectivity was driven by the southwest and northeast main barotropic circulation structures, with high retention levels in both. Destination locations, spawning sites and PLD were the main drivers of potential connectivity, explaining respectively 26%, 59% and 5% of the variance. Differences between potential and realistic connectivity showed the significant contribution of the pearl oyster broodstock location to its own dynamics. Realistic connectivity showed larger larval supply in the western destination locations, which are preferentially used by farmers for spat collection. In addition, larval supply in the same sectors was enhanced during summer wind conditions. These results provide new cues to understanding the dynamics of bottom-dwelling populations in atoll lagoons, and show how to take advantage of numerical models for pearl oyster management.

  17. Larval Dispersal Modeling of Pearl Oyster Pinctada margaritifera following Realistic Environmental and Biological Forcing in Ahe Atoll Lagoon

    Science.gov (United States)

    Thomas, Yoann; Dumas, Franck; Andréfouët, Serge

    2014-01-01

    Studying the larval dispersal of bottom-dwelling species is necessary to understand their population dynamics and optimize their management. The black-lip pearl oyster (Pinctada margaritifera) is cultured extensively to produce black pearls, especially in French Polynesia's atoll lagoons. This aquaculture relies on spat collection, a process that can be optimized by understanding which factors influence larval dispersal. Here, we investigate the sensitivity of P. margaritifera larval dispersal kernel to both physical and biological factors in the lagoon of Ahe atoll. Specifically, using a validated 3D larval dispersal model, the variability of lagoon-scale connectivity is investigated against wind forcing, depth and location of larval release, destination location, vertical swimming behavior and pelagic larval duration (PLD) factors. The potential connectivity was spatially weighted according to both the natural and cultivated broodstock densities to provide a realistic view of connectivity. We found that the mean pattern of potential connectivity was driven by the southwest and northeast main barotropic circulation structures, with high retention levels in both. Destination locations, spawning sites and PLD were the main drivers of potential connectivity, explaining respectively 26%, 59% and 5% of the variance. Differences between potential and realistic connectivity showed the significant contribution of the pearl oyster broodstock location to its own dynamics. Realistic connectivity showed larger larval supply in the western destination locations, which are preferentially used by farmers for spat collection. In addition, larval supply in the same sectors was enhanced during summer wind conditions. These results provide new cues to understanding the dynamics of bottom-dwelling populations in atoll lagoons, and show how to take advantage of numerical models for pearl oyster management. PMID:24740288

  18. Mathematics Instructional Model Based on Realistic Mathematics Education to Promote Problem Solving Ability at Junior High School Padang

    Directory of Open Access Journals (Sweden)

    Edwin Musdi

    2016-02-01

    Full Text Available This research aims to develop a mathematics instructional model based realistic mathematics education (RME to promote students' problem-solving abilities. The design research used Plomp models, which consists of preliminary phase, development or proto-typing phase and assessment phase.  At this study, only the first two phases conducted. The first phase, a preliminary investigation, carried out with a literature study to examine the theory-based instructional learning RME model, characteristics of learners, learning management descriptions by junior high school mathematics teacher and relevant research. The development phase is done by developing a draft model (an early prototype model that consists of the syntax, the social system, the principle of reaction, support systems, and the impact and effects of instructional support. Early prototype model contain a draft model, lesson plans, worksheets, and assessments. Tesssmer formative evaluation model used to revise the model. In this study only phase of one to one evaluation conducted. In the ppreliminary phase has produced a theory-based learning RME model, a description of the characteristics of learners in grade VIII Junior High School Padang and the description of teacher teaching in the classroom. The result showed that most students were still not be able to solve the non-routine problem. Teachers did not optimally facilitate students to develop problem-solving skills of students. It was recommended that the model can be applied in the classroom.

  19. Dynamic force matching: Construction of dynamic coarse-grained models with realistic short time dynamics and accurate long time dynamics

    Science.gov (United States)

    Davtyan, Aram; Voth, Gregory A.; Andersen, Hans C.

    2016-12-01

    We recently developed a dynamic force matching technique for converting a coarse-grained (CG) model of a molecular system, with a CG potential energy function, into a dynamic CG model with realistic dynamics [A. Davtyan et al., J. Chem. Phys. 142, 154104 (2015)]. This is done by supplementing the model with additional degrees of freedom, called "fictitious particles." In that paper, we tested the method on CG models in which each molecule is coarse-grained into one CG point particle, with very satisfactory results. When the method was applied to a CG model of methanol that has two CG point particles per molecule, the results were encouraging but clearly required improvement. In this paper, we introduce a new type (called type-3) of fictitious particle that exerts forces on the center of mass of two CG sites. A CG model constructed using type-3 fictitious particles (as well as type-2 particles previously used) gives a much more satisfactory dynamic model for liquid methanol. In particular, we were able to construct a CG model that has the same self-diffusion coefficient and the same rotational relaxation time as an all-atom model of liquid methanol. Type-3 particles and generalizations of it are likely to be useful in converting more complicated CG models into dynamic CG models.

  20. Mathematics Instructional Model Based on Realistic Mathematics Education to Promote Problem Solving Ability at Junior High School Padang

    Directory of Open Access Journals (Sweden)

    Edwin Musdi

    2016-02-01

    Full Text Available This research aims to develop a mathematics instructional model based realistic mathematics education (RME to promote students' problem-solving abilities. The design research used Plomp models, which consists of preliminary phase, development or proto-typing phase and assessment phase.  At this study, only the first two phases conducted. The first phase, a preliminary investigation, carried out with a literature study to examine the theory-based instructional learning RME model, characteristics of learners, learning management descriptions by junior high school mathematics teacher and relevant research. The development phase is done by developing a draft model (an early prototype model that consists of the syntax, the social system, the principle of reaction, support systems, and the impact and effects of instructional support. Early prototype model contain a draft model, lesson plans, worksheets, and assessments. Tesssmer formative evaluation model used to revise the model. In this study only phase of one to one evaluation conducted. In the ppreliminary phase has produced a theory-based learning RME model, a description of the characteristics of learners in grade VIII Junior High School Padang and the description of teacher teaching in the classroom. The result showed that most students were still not be able to solve the non-routine problem. Teachers did not optimally facilitate students to develop problem-solving skills of students. It was recommended that the model can be applied in the classroom.

  1. Effect of Anatomically Realistic Full-Head Model on Activation of Cortical Neurons in Subdural Cortical Stimulation—A Computational Study

    Science.gov (United States)

    Seo, Hyeon; Kim, Donghyeon; Jun, Sung Chan

    2016-06-01

    Electrical brain stimulation (EBS) is an emerging therapy for the treatment of neurological disorders, and computational modeling studies of EBS have been used to determine the optimal parameters for highly cost-effective electrotherapy. Recent notable growth in computing capability has enabled researchers to consider an anatomically realistic head model that represents the full head and complex geometry of the brain rather than the previous simplified partial head model (extruded slab) that represents only the precentral gyrus. In this work, subdural cortical stimulation (SuCS) was found to offer a better understanding of the differential activation of cortical neurons in the anatomically realistic full-head model than in the simplified partial-head models. We observed that layer 3 pyramidal neurons had comparable stimulation thresholds in both head models, while layer 5 pyramidal neurons showed a notable discrepancy between the models; in particular, layer 5 pyramidal neurons demonstrated asymmetry in the thresholds and action potential initiation sites in the anatomically realistic full-head model. Overall, the anatomically realistic full-head model may offer a better understanding of layer 5 pyramidal neuronal responses. Accordingly, the effects of using the realistic full-head model in SuCS are compelling in computational modeling studies, even though this modeling requires substantially more effort.

  2. Esophageal Inlet Patch

    Directory of Open Access Journals (Sweden)

    C. Behrens

    2011-01-01

    Full Text Available An inlet patch is a congenital anomaly consisting of ectopic gastric mucosa at or just distal to the upper esophageal sphincter. Most inlet patches are largely asymptomatic, but in problematic cases complications related to acid secretion such as esophagitis, ulcer, web and stricture may occur. The diagnosis of inlet patch is strongly suggested on barium swallow where the most common pattern consists of two small indentations on the wall of the esophagus. The diagnosis of inlet patch is confirmed via endoscopy with biopsy. At endoscopy, the lesion appears salmon-coloured and velvety and is easily distinguished from the normal grey-white squamous epithelium of the esophagus. The prominent margins correlate with the radiological findings of indentations and rim-like shadows on barium swallow. Histopathology provides the definitive diagnosis by demonstrating gastric mucosa adjacent to normal esophageal mucosa. No treatment is required for asymptomatic inlet patches. Symptomatic cases are treated with proton pump inhibitors to relieve symptoms related to acid secretion. Strictures and webs are treated with serial dilatation and should be biopsied to rule out malignancy.

  3. Design and validation of realistic breast models for use in multiple alternative forced choice virtual clinical trials.

    Science.gov (United States)

    Elangovan, Premkumar; Mackenzie, Alistair; Dance, David R; Young, Kenneth C; Cooke, Victoria; Wilkinson, Louise; Given-Wilson, Rosalind M; Wallis, Matthew G; Wells, Kevin

    2017-04-07

    A novel method has been developed for generating quasi-realistic voxel phantoms which simulate the compressed breast in mammography and digital breast tomosynthesis (DBT). The models are suitable for use in virtual clinical trials requiring realistic anatomy which use the multiple alternative forced choice (AFC) paradigm and patches from the complete breast image. The breast models are produced by extracting features of breast tissue components from DBT clinical images including skin, adipose and fibro-glandular tissue, blood vessels and Cooper's ligaments. A range of different breast models can then be generated by combining these components. Visual realism was validated using a receiver operating characteristic (ROC) study of patches from simulated images calculated using the breast models and from real patient images. Quantitative analysis was undertaken using fractal dimension and power spectrum analysis. The average areas under the ROC curves for 2D and DBT images were 0.51  ±  0.06 and 0.54  ±  0.09 demonstrating that simulated and real images were statistically indistinguishable by expert breast readers (7 observers); errors represented as one standard error of the mean. The average fractal dimensions (2D, DBT) for real and simulated images were (2.72  ±  0.01, 2.75  ±  0.01) and (2.77  ±  0.03, 2.82  ±  0.04) respectively; errors represented as one standard error of the mean. Excellent agreement was found between power spectrum curves of real and simulated images, with average β values (2D, DBT) of (3.10  ±  0.17, 3.21  ±  0.11) and (3.01  ±  0.32, 3.19  ±  0.07) respectively; errors represented as one standard error of the mean. These results demonstrate that radiological images of these breast models realistically represent the complexity of real breast structures and can be used to simulate patches from mammograms and DBT images that are indistinguishable from

  4. Design and validation of realistic breast models for use in multiple alternative forced choice virtual clinical trials

    Science.gov (United States)

    Elangovan, Premkumar; Mackenzie, Alistair; Dance, David R.; Young, Kenneth C.; Cooke, Victoria; Wilkinson, Louise; Given-Wilson, Rosalind M.; Wallis, Matthew G.; Wells, Kevin

    2017-04-01

    A novel method has been developed for generating quasi-realistic voxel phantoms which simulate the compressed breast in mammography and digital breast tomosynthesis (DBT). The models are suitable for use in virtual clinical trials requiring realistic anatomy which use the multiple alternative forced choice (AFC) paradigm and patches from the complete breast image. The breast models are produced by extracting features of breast tissue components from DBT clinical images including skin, adipose and fibro-glandular tissue, blood vessels and Cooper’s ligaments. A range of different breast models can then be generated by combining these components. Visual realism was validated using a receiver operating characteristic (ROC) study of patches from simulated images calculated using the breast models and from real patient images. Quantitative analysis was undertaken using fractal dimension and power spectrum analysis. The average areas under the ROC curves for 2D and DBT images were 0.51  ±  0.06 and 0.54  ±  0.09 demonstrating that simulated and real images were statistically indistinguishable by expert breast readers (7 observers); errors represented as one standard error of the mean. The average fractal dimensions (2D, DBT) for real and simulated images were (2.72  ±  0.01, 2.75  ±  0.01) and (2.77  ±  0.03, 2.82  ±  0.04) respectively; errors represented as one standard error of the mean. Excellent agreement was found between power spectrum curves of real and simulated images, with average β values (2D, DBT) of (3.10  ±  0.17, 3.21  ±  0.11) and (3.01  ±  0.32, 3.19  ±  0.07) respectively; errors represented as one standard error of the mean. These results demonstrate that radiological images of these breast models realistically represent the complexity of real breast structures and can be used to simulate patches from mammograms and DBT images that are indistinguishable from

  5. Towards a Realistic, Data-Driven Thermodynamic MHD Model of the Global Solar Corona

    CERN Document Server

    Downs, Cooper; van der Holst, Bart; Lugaz, Noé; Sokolov, Igor V; Gombosi, Tamas I

    2009-01-01

    In this work we describe our implementation of a thermodynamic energy equation into the global corona model of the Space Weather Modeling Framework (SWMF), and its development into the new Lower Corona (LC) model. This work includes the integration of the additional energy transport terms of coronal heating, electron heat conduction, and optically thin radiative cooling into the governing magnetohydrodynamic (MHD) energy equation. We examine two different boundary conditions using this model; one set in the upper transition region (the Radiative Energy Balance model), as well as a uniform chromospheric condition where the transition region can be modeled in its entirety. Via observation synthesis from model results and the subsequent comparison to full sun extreme ultraviolet (EUV) and soft X-Ray observations of Carrington Rotation (CR) 1913 centered on Aug 27, 1996, we demonstrate the need for these additional considerations when using global MHD models to describe the unique conditions in the low corona. Th...

  6. Effective electric fields along realistic DTI-based neural trajectories for modelling the stimulation mechanisms of TMS.

    Science.gov (United States)

    De Geeter, N; Crevecoeur, G; Leemans, A; Dupré, L

    2015-01-21

    In transcranial magnetic stimulation (TMS), an applied alternating magnetic field induces an electric field in the brain that can interact with the neural system. It is generally assumed that this induced electric field is the crucial effect exciting a certain region of the brain. More specifically, it is the component of this field parallel to the neuron's local orientation, the so-called effective electric field, that can initiate neuronal stimulation. Deeper insights on the stimulation mechanisms can be acquired through extensive TMS modelling. Most models study simple representations of neurons with assumed geometries, whereas we embed realistic neural trajectories computed using tractography based on diffusion tensor images. This way of modelling ensures a more accurate spatial distribution of the effective electric field that is in addition patient and case specific. The case study of this paper focuses on the single pulse stimulation of the left primary motor cortex with a standard figure-of-eight coil. Including realistic neural geometry in the model demonstrates the strong and localized variations of the effective electric field between the tracts themselves and along them due to the interplay of factors such as the tract's position and orientation in relation to the TMS coil, the neural trajectory and its course along the white and grey matter interface. Furthermore, the influence of changes in the coil orientation is studied. Investigating the impact of tissue anisotropy confirms that its contribution is not negligible. Moreover, assuming isotropic tissues lead to errors of the same size as rotating or tilting the coil with 10 degrees. In contrast, the model proves to be less sensitive towards the not well-known tissue conductivity values.

  7. Coupled Mesoscale-Large-Eddy Modeling of Realistic Stable Boundary Layer Turbulence

    CERN Document Server

    Wang, Yao; Manuel, Lance

    2013-01-01

    Site-specific flow and turbulence information are needed for various practical applications, ranging from aerodynamic/aeroelastic modeling for wind turbine design to optical diffraction calculations. Even though highly desirable, collecting on-site meteorological measurements can be an expensive, time-consuming, and sometimes a challenging task. In this work, we propose a coupled mesoscale-large-eddy modeling framework to synthetically generate site-specific flow and turbulence data. The workhorses behind our framework are a state-of-the-art, open-source atmospheric model called the Weather Research and Forecasting (WRF) model and a tuning-free large-eddy simulation (LES) model. Using this coupled framework, we simulate a nighttime stable boundary layer (SBL) case from the well-known CASES-99 field campaign. One of the unique aspects of this work is the usage of a diverse range of observations for characterization and validation. The coupled models reproduce certain characteristics of observed low-level jets....

  8. Doping Dependent Charge Transfer Gap and Realistic Electronic Model of n-type Cuprate Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, T.

    2010-05-03

    Based on the analysis of the measurement data of angle-resolved photoemission spectroscopy (ARPES) and optics, we show that the charge transfer gap is significantly smaller than the optical one and is reduced by doping in electron doped cuprate superconductors. This leads to a strong charge fluctuation between the Zhang-Rice singlet and the upper Hubbard bands. The basic model for describing this system is a hybridized two-band t-J model. In the symmetric limit where the corresponding intra- and inter-band hopping integrals are equal to each other, this two-band model is equivalent to the Hubbard model with an antiferromagnetic exchange interaction (i.e. the t-U-J model). The mean-field result of the t-U-J model gives a good account for the doping evolution of the Fermi surface and the staggered magnetization.

  9. Pursuing realistic hydrologic model under SUPERFLEX framework in a semi-humid catchment in China

    Science.gov (United States)

    Wei, Lingna; Savenije, Hubert H. G.; Gao, Hongkai; Chen, Xi

    2016-04-01

    Model realism is pursued perpetually by hydrologists for flood and drought prediction, integrated water resources management and decision support of water security. "Physical-based" distributed hydrologic models are speedily developed but they also encounter unneglectable challenges, for instance, computational time with low efficiency and parameters uncertainty. This study step-wisely tested four conceptual hydrologic models under the framework of SUPERFLEX in a small semi-humid catchment in southern Huai River basin of China. The original lumped FLEXL has hypothesized model structure of four reservoirs to represent canopy interception, unsaturated zone, subsurface flow of fast and slow components and base flow storage. Considering the uneven rainfall in space, the second model (FLEXD) is developed with same parameter set for different rain gauge controlling units. To reveal the effect of topography, terrain descriptor of height above the nearest drainage (HAND) combined with slope is applied to classify the experimental catchment into two landscapes. Then the third one (FLEXTOPO) builds different model blocks in consideration of the dominant hydrologic process corresponding to the topographical condition. The fourth one named FLEXTOPOD integrating the parallel framework of FLEXTOPO in four controlled units is designed to interpret spatial variability of rainfall patterns and topographic features. Through pairwise comparison, our results suggest that: (1) semi-distributed models (FLEXD and FLEXTOPOD) taking precipitation spatial heterogeneity into account has improved model performance with parsimonious parameter set, and (2) hydrologic model architecture with flexibility to reflect perceived dominant hydrologic processes can include the local terrain circumstances for each landscape. Hence, the modeling actions are coincided with the catchment behaviour and close to the "reality". The presented methodology is regarding hydrologic model as a tool to test our

  10. Confirmation of a realistic reactor model for BNCT dosimetry at the TRIGA Mainz

    Energy Technology Data Exchange (ETDEWEB)

    Ziegner, Markus, E-mail: Markus.Ziegner.fl@ait.ac.at [AIT Austrian Institute of Technology GmbH, Vienna A-1220, Austria and Institute of Atomic and Subatomic Physics, Vienna University of Technology, Vienna A-1020 (Austria); Schmitz, Tobias; Hampel, Gabriele [Institut für Kernchemie, Johannes Gutenberg-Universität, Mainz DE-55128 (Germany); Khan, Rustam [Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad PK-44000 (Pakistan); Blaickner, Matthias [AIT Austrian Institute of Technology GmbH, Vienna A-1220 (Austria); Palmans, Hugo [Acoustics and Ionising Radiation Division, National Physical Laboratory, Teddington TW11 0LW, United Kingdom and Medical Physics Group, EBG MedAustron GmbH, Wiener Neustadt A-2700 (Austria); Sharpe, Peter [Acoustics and Ionising Radiation Division, National Physical Laboratory, Teddington TW11 0LW (United Kingdom); Böck, Helmuth [Institute of Atomic and Subatomic Physics, Vienna University of Technology, Vienna A-1020 (Austria)

    2014-11-01

    Purpose: In order to build up a reliable dose monitoring system for boron neutron capture therapy (BNCT) applications at the TRIGA reactor in Mainz, a computer model for the entire reactor was established, simulating the radiation field by means of the Monte Carlo method. The impact of different source definition techniques was compared and the model was validated by experimental fluence and dose determinations. Methods: The depletion calculation code ORIGEN2 was used to compute the burn-up and relevant material composition of each burned fuel element from the day of first reactor operation to its current core. The material composition of the current core was used in a MCNP5 model of the initial core developed earlier. To perform calculations for the region outside the reactor core, the model was expanded to include the thermal column and compared with the previously established ATTILA model. Subsequently, the computational model is simplified in order to reduce the calculation time. Both simulation models are validated by experiments with different setups using alanine dosimetry and gold activation measurements with two different types of phantoms. Results: The MCNP5 simulated neutron spectrum and source strength are found to be in good agreement with the previous ATTILA model whereas the photon production is much lower. Both MCNP5 simulation models predict all experimental dose values with an accuracy of about 5%. The simulations reveal that a Teflon environment favorably reduces the gamma dose component as compared to a polymethyl methacrylate phantom. Conclusions: A computer model for BNCT dosimetry was established, allowing the prediction of dosimetric quantities without further calibration and within a reasonable computation time for clinical applications. The good agreement between the MCNP5 simulations and experiments demonstrates that the ATTILA model overestimates the gamma dose contribution. The detailed model can be used for the planning of structural

  11. Construction of Realistic Scene in Virtual Turning Based on Global Illumination Model and Chip Simulation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    With the rapid development of manufacturing technology, the traditional simulation of machining can not meet the people's need. Research on virtual machining environment is one of the key parts of virtual manufacturing technology. According to the features of virtual turning, this paper proposes a simplified Whitted lighting model based on analysis of Phong and other local illumination model. This model takes the material and roughness of workpiece into account to calculate the roughness coefficient D, geom...

  12. Validation of airway resistance models for predicting pressure loss through anatomically realistic conducting airway replicas of adults and children.

    Science.gov (United States)

    Borojeni, Azadeh A T; Noga, Michelle L; Martin, Andrew R; Finlay, Warren H

    2015-07-16

    This work describes in vitro measurement of the total pressure loss at varying flow rate through anatomically realistic conducting airway replicas of 10 children, 4 to 8 years old, and 5 adults. Experimental results were compared with analytical predictions made using published airway resistance models. For the adult replicas, the model proposed by van Ertbruggen et al. (2005. J. Appl. Physiol. 98, 970-980) most accurately predicted central conducting airway resistance for inspiratory flow rates ranging from 15 to 90 L/min. Models proposed by Pedley et al. (1970. J. Respir. Physiol. 9, 371-386) and by Katz et al. (2011. J. Biomech. 44, 1137-1143) also provided reasonable estimates, but with a tendency to over predict measured pressure loss for both models. For child replicas, the Pedley and Katz models both provided good estimation of measured pressure loss at flow rates representative of resting tidal breathing, but under predicted measured values at high inspiratory flow rate (60 L/min). The van Ertbruggen model, developed based on flow simulations performed in an adult airway model, tended to under predict measured pressure loss through the child replicas across the range of flow rates studied (2 to 60 L/min). These results are intended to provide guidance for selection of analytical pressure loss models for use in predicting airway resistance and ventilation distribution in adults and children. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Realistic f(T) model describing the de Sitter epoch of the dark energy dominated universe

    CERN Document Server

    Nassur, S B; Rodrigues, M E; Houndjo, M J S; Tossa, J

    2015-01-01

    We consider an exponential model within the so-called f(T) theory of gravity, where $T$ denotes the torsion scalar. We focus our work on a cosmological feature of such a model, checking whether it may describe the de Sitter stage of the current universe through the analysis of the redshift z. Our results shows that the model reproduces the de Sitter stage only for low-redshifts, where the perturbation function goes toward zero as the low values of the redshift are reached, whereas the effective parameter of equation of state goes to -1, which is the expected behavior for any model able to reproduce de Sitter stage.

  14. Investigation of realistic PET simulations incorporating tumor patient's specificity using anthropomorphic models: creation of an oncology database.

    Science.gov (United States)

    Papadimitroulas, Panagiotis; Loudos, George; Le Maitre, Amandine; Hatt, Mathieu; Tixier, Florent; Efthimiou, Nikos; Nikiforidis, George C; Visvikis, Dimitris; Kagadis, George C

    2013-11-01

    The GATE Monte Carlo simulation toolkit is used for the implementation of realistic PET simulations incorporating tumor heterogeneous activity distributions. The reconstructed patient images include noise from the acquisition process, imaging system's performance restrictions and have limited spatial resolution. For those reasons, the measured intensity cannot be simply introduced in GATE simulations, to reproduce clinical data. Investigation of the heterogeneity distribution within tumors applying partial volume correction (PVC) algorithms was assessed. The purpose of the present study was to create a simulated oncology database based on clinical data with realistic intratumor uptake heterogeneity properties. PET/CT data of seven oncology patients were used in order to create a realistic tumor database investigating the heterogeneity activity distribution of the simulated tumors. The anthropomorphic models (NURBS based cardiac torso and Zubal phantoms) were adapted to the CT data of each patient, and the activity distribution was extracted from the respective PET data. The patient-specific models were simulated with the Monte Carlo Geant4 application for tomography emission (GATE) in three different levels for each case: (a) using homogeneous activity within the tumor, (b) using heterogeneous activity distribution in every voxel within the tumor as it was extracted from the PET image, and (c) using heterogeneous activity distribution corresponding to the clinical image following PVC. The three different types of simulated data in each case were reconstructed with two iterations and filtered with a 3D Gaussian postfilter, in order to simulate the intratumor heterogeneous uptake. Heterogeneity in all generated images was quantified using textural feature derived parameters in 3D according to the ground truth of the simulation, and compared to clinical measurements. Finally, profiles were plotted in central slices of the tumors, across lines with heterogeneous

  15. Realistic Modeling and Animation of Human Body Based on Scanned Data

    Institute of Scientific and Technical Information of China (English)

    Yong-You Ma; Hui Zhang; Shou-Wei Jiang

    2004-01-01

    In this paper we propose a novel method for building animation model of real human body from surface scanned data.The human model is represented by a triangular mesh and described as a layered geometric model.The model consists of two layers: the control skeleton generating body animation from motion capture data,and the simplified surface model providing an efficient representation of the skin surface shape.The skeleton is generated automatically from surface scanned data using the feature extraction,and thena point-to-line mapping is used to map the surface model onto the underlying skeleton.The resulting model enables real-time and smooth animation by manipulation of the skeleton while maintaining the surface detail.Compared with earlier approach,the principal advantages of our approach are the automated generation of body control skeletons from the scanned data for real-time animation,and the automatic mapping and animation of the captured human surface shape.The human model constructed in this work can be used for applications of ergonomic design,garment CAD,real-time simulating humans in virtual reality environment and so on.

  16. A Semi-Analytical Target Strength Model for Active Sonar Performance in Realistic Propagation Conditions

    NARCIS (Netherlands)

    Schippers, P.; Volker, A.W.F.; Golliard, J.; Jong, C. de

    2006-01-01

    Propagation and sonar performance are modelled by TNO’s ALMOST program, already being developed since the Eighties. It models propagation between sonar and target based on ray theory, including effects of sediment bottoms, reverberation and ambient noise. Moreover, antenna directivity (beam forming)

  17. Solar system tests for realistic $f(T)$ models with nonminimal torsion-matter coupling

    CERN Document Server

    Lin, Rui-Hui; Li, Xin-Zhou

    2016-01-01

    In the previous paper, we have constructed two $f(T)$ models with nonminimal torsion-matter coupling extension, which are successful in describing the evolution history of the Universe including the radiation-dominated era, the matter-dominated era, and the present accelerating expansion. Meantime, the significant advantage of these models is that they could avoid the cosmological constant problem of $\\Lambda$CDM. However, the nonminimal coupling between matter and torsion will affect the tests of Solar system. In this paper, we study the effects of Solar system in these models, including the gravitation redshift, geodetic effect and perihelion preccesion. We find that Model I can pass all three of the Solar system tests. For Model II, the parameter is constrained by the measure of the perihelion precession of Mercury.

  18. Gasification of biomass in a fixed bed downdraft gasifier--a realistic model including tar.

    Science.gov (United States)

    Barman, Niladri Sekhar; Ghosh, Sudip; De, Sudipta

    2012-03-01

    This study presents a model for fixed bed downdraft biomass gasifiers considering tar also as one of the gasification products. A representative tar composition along with its mole fractions, as available in the literature was used as an input parameter within the model. The study used an equilibrium approach for the applicable gasification reactions and also considered possible deviations from equilibrium to further upgrade the equilibrium model to validate a range of reported experimental results. Heat balance was applied to predict the gasification temperature and the predicted values were compared with reported results in literature. A comparative study was made with some reference models available in the literature and also with experimental results reported in the literature. Finally a predicted variation of performance of the gasifier by this validated model for different air-fuel ratio and moisture content was also discussed.

  19. Toward more realistic projections of soil carbon dynamics by Earth system models

    Science.gov (United States)

    Luo, Y.; Ahlström, Anders; Allison, Steven D.; Batjes, Niels H.; Brovkin, V.; Carvalhais, Nuno; Chappell, Adrian; Ciais, Philippe; Davidson, Eric A.; Finzi, Adien; Georgiou, Katerina; Guenet, Bertrand; Hararuk, Oleksandra; Harden, Jennifer; He, Yujie; Hopkins, Francesca; Jiang, L.; Koven, Charles; Jackson, Robert B.; Jones, Chris D.; Lara, M.; Liang, J.; McGuire, Anthony; Parton, William; Peng, Changhui; Randerson, J.; Salazar, Alejandro; Sierra, Carlos A.; Smith, Matthew J.; Tian, Hanqin; Todd-Brown, Katherine E. O; Torn, Margaret S.; van Groenigen, Kees Jan; Wang, Ying; West, Tristram O.; Wei, Yaxing; Wieder, William R.; Xia, Jianyang; Xu, Xia; Xu, Xiaofeng; Zhou, T.

    2016-01-01

    Soil carbon (C) is a critical component of Earth system models (ESMs), and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the third to fifth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. First, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by first-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic soil organic C (SOC) dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Second, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based data sets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Third, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable data sets are available to select the most representative model structure

  20. A Realistic Process Example for MIMO MPC based on Autoregressive Models

    DEFF Research Database (Denmark)

    Huusom, Jakob Kjøbsted; Jørgensen, John Bagterp

    2014-01-01

    Advanced controllers such as model predictive control are i n use for a wide range of application in the process industry. The potential utili zation of such advanced predictive controllers is far from exhausted. One barrier for more wide spread implementation is the lack of simple methodologies...... for advanced control design develo pment which may be used by non experts in control theory. This paper presents and illustra tes the use of a simple methodology to design an offset-free MPC based on ARX models. Hence a mecha nistic process model is not required. The forced circulation evaporator by Newell...

  1. Validation of Tilt Gain under Realistic Path Loss Model and Network Scenario

    DEFF Research Database (Denmark)

    Nguyen, Huan Cong; Rodriguez, Ignacio; Sørensen, Troels Bundgaard

    2013-01-01

    Despite being a simple and commonly-applied radio optimization technique, the impact on practical network performance from base station antenna downtilt is not well understood. Most published studies based on empirical path loss models report tilt angles and performance gains that are far higher...... than practical experience suggests. We motivate in this paper, based on a practical LTE scenario, that the discrepancy partly lies in the path loss model, and shows that a more detailed semi-deterministic model leads to both lower gains in terms of SINR, outage probability and downlink throughput...... settings, including the use of electrical and/or mechanical antenna downtilt, and therefore it is possible to find multiple optimum tilt profiles in a practical case. A broader implication of this study is that care must be taken when using the 3GPP model to evaluate advanced adaptive antenna techniques...

  2. SMART-DS: Synthetic Models for Advanced, Realistic Testing: Distribution Systems and Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Palmintier, Bryan: Hodge, Bri-Mathias

    2017-01-26

    This presentation provides a Smart-DS project overview and status update for the ARPA-e GRID DATA program meeting 2017, including distribution systems, models, and scenarios, as well as opportunities for GRID DATA collaborations.

  3. 750 GeV diphoton excesses in a realistic D-brane model

    Science.gov (United States)

    Li, Tianjun; Maxin, James A.; Mayes, Van E.; Nanopoulos, Dimitri V.

    2016-07-01

    We study the diphoton excesses near 750 GeV recently reported by the ATLAS and CMS collaborations within the context of a phenomenologically interesting intersecting/magnetized D-brane model on a toroidal orientifold. It is shown that the model contains a Standard Model singlet scalar as well as vector-like quarks and leptons. In addition, it is shown that the singlet scalar has Yukawa couplings with vector-like quarks and leptons such that it may be produced in proton-proton collisions via gluon fusion as well as decay to diphotons through loops involving the vector-like quarks. Moreover, the required vector-like quarks and leptons may appear in complete S U (5 ) multiplets so that gauge coupling unification may be maintained. Finally, it is shown that the diphoton signal may be accommodated within the model.

  4. Modeling and Control of Aggregated Air Conditioning Loads Under Realistic Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chin-Yao; Zhang, Wei; Lian, Jianming; Kalsi, Karanjit

    2013-02-24

    Demand-side control is playing an increasingly important role in smart grid control strategies. Modeling the dynamical behavior of a large population of appliances is especially important to evaluate the effectiveness of various load control strategies. In this paper, a high accuracy aggregated model is first developed for a population of HVAC units. The model efficiently includes statistical information of the population, systematically deals with heterogeneity, and accounts for a second-order effect necessary to accurately capture the transient dynamics in the collective response. Furthermore, the model takes into account the lockout effect of the compressor in order to represent the dynamics of the system under control more accurately. Then, a novel closed loop load control strategy is designed to track a desired demand curve and to ensure a stable and smooth response.

  5. A theoretical model for mid- and low-latitude ionospheric electric fields in realistic geomagnetic fields

    Institute of Scientific and Technical Information of China (English)

    REN ZhiPeng; WAN WeiXing; WEI Yong; LIU LiBo; YU Tao

    2008-01-01

    The geomagnetic fields, which play important roles in the ionospheric dynamo, can greatly affect the global distribution of ionospheric electric fields, currents and other ionospheric electrodynamics phenomena. In the study of ionospheric electrodynamics phenomena, such as the longitudinal variations of ionospheric electric fields, the non-dipolar component of the geomagnetic fields must be taken into account. In this paper, we deduce a theoretical electric field model for ionospheric dynamo at midand low-latitude which adopt a modified magnetic apex coordinates system. In the new electric field model, the geomagnetic fields can be calculated from either the IGRF model or the dipole field model,and the neutral winds and conductivities are calculated based on empirical models. Then the dynamo equation for the electric potential is finally solved in terms of the line-by-line iteration method, and the ionospheric electric fields and currents are derived from the calculated potential. Our model can reproduce the main features of the ionospheric electrodynamics processes, so it will be a useful tool for the investigation of the upper atmosphere and ionosphere.

  6. Anatomically realistic multiscale models of normal and abnormal gastrointestinal electrical activity.

    Science.gov (United States)

    Cheng, Leo K; Komuro, Rie; Austin, Travis M; Buist, Martin L; Pullan, Andrew J

    2007-03-01

    One of the major aims of the International Union of Physiological Sciences (IUPS) Physiome Project is to develop multiscale mathematical and computer models that can be used to help understand human health. We present here a small facet of this broad plan that applies to the gastrointestinal system. Specifically, we present an anatomically and physiologically based modelling framework that is capable of simulating normal and pathological electrical activity within the stomach and small intestine. The continuum models used within this framework have been created using anatomical information derived from common medical imaging modalities and data from the Visible Human Project. These models explicitly incorporate the various smooth muscle layers and networks of interstitial cells of Cajal (ICC) that are known to exist within the walls of the stomach and small bowel. Electrical activity within individual ICCs and smooth muscle cells is simulated using a previously published simplified representation of the cell level electrical activity. This simulated cell level activity is incorporated into a bidomain representation of the tissue, allowing electrical activity of the entire stomach or intestine to be simulated in the anatomically derived models. This electrical modelling framework successfully replicates many of the qualitative features of the slow wave activity within the stomach and intestine and has also been used to investigate activity associated with functional uncoupling of the stomach.

  7. Anatomically realistic multiscale models of normal and abnormal gastrointestinal electrical activity

    Institute of Scientific and Technical Information of China (English)

    Leo K Cheng; Rie Komuro; Travis M Austin; Martin L Buist; Andrew J Pullan

    2007-01-01

    One of the major aims of the Tnternational Union of Physiological Sciences (IUPS) Physiome Project is to develop multiscale mathematical and computer models that can be used to help understand human health.We present here a small facet of this broad plan that applies to the gastrointestinal system. Specifically,we present an anatomically and physiologically based modelling framework that is capable of simulating normal and pathological electrical activity within the stomach and small intestine. The continuum models used within this framework have been created using anatomical information derived from common medical imaging modalities and data from the Visible Human Project. These models explicitly incorporate the various smooth muscle layers and networks of interstitial cells of Cajal (ICC) that are known to exist within the walls of the stomach and small bowel. Electrical activity within individual ICCs and smooth muscle cells is simulated using a previously published simplified representation of the cell level electrical activity. This simulated cell level activity is incorporated into a bidomain representation of the tissue, allowing electrical activity of the entire stomach or intestine to be simulated in the anatomically derived models. This electrical modelling framework successfully replicates many of the qualitative features of the slow wave activity within the stomach and intestine and has also been used to investigate activity associated with functional uncoupling of the stomach.

  8. Towards realistic $f(T)$ models with nonminimal torsion-matter coupling extension

    CERN Document Server

    Feng, Chao-jun; Li, Xin-zhou; Lin, Rui-hui; Zhai, Xiang-hua

    2015-01-01

    Using the observation data of SNeIa, CMB and BAO, we establish two concrete $f(T)$ models with nonminimal torsion-matter coupling extension. We study in detail the cosmological implication of our models and find they are successful in describing the observation of the Universe, its large scale structure and evolution. In other words, these models do not change the successful aspects of $\\Lambda$CDM scenario under the error band of fitting values as describing the evolution history of the Universe including radiation-dominated era, matter-dominated era and the present accelerating expansion. Meanwhile, the significant advantage of these models is that they could avoid the cosmological constant problem of $\\Lambda$CDM. A joint analysis is performed by using the data of CMB+BAO+JLA, which leads to $\\Omega_{m0}=0.255\\pm 0.010, \\Omega_{b0}h^2=0.0221\\pm 0.0003$ and $H_0=68.54\\pm 1.27$ for model I and $\\Omega_{m0}=0.306\\pm 0.010, \\Omega_{b0}h^2=0.0225\\pm 0.0003$ and $H_0=60.97\\pm 0.44$ for model II at 1$\\sigma$ conf...

  9. The effect of fixture neck design in a realistic model of dental implant: a finite element approach.

    Science.gov (United States)

    Necchi, Silvia; Migliavacca, Francesco; Gastaldi, Dario; Pizzagalli, Manuela; Del Fabbro, Massimo; Weinstein, Roberto; Pietrabissa, Riccardo; Dubini, Gabriele

    2003-01-01

    The aim of this work is to develop an accurate finite element model able to reproduce a standard experimental set-up for the evaluation of mechanical failure of a dental implant system. The considered system is composed of a fixture, an abutment and a connecting screw. We analysed the behaviour of the implant system considering three different designs of the fixture, in order to establish which one provides the better mechanical behaviour. After the definition of the numerical models, loading conditions were selected in order to reproduce the same stress state found in previous mechanical failure tests. Preloading and functional loading conditions were simulated. The analysis of the numerical results shows that the structure yielding is due to the fixture neck plastic deformation, that increases the load eccentricity and then the bending stress on the connecting screw. Only slight differences were found between the three implant systems in the amount and distribution of stress. The model reproduces properly the implant systems and the experimental set-up. The goodness of the model can be summarised as: realistic geometrical structure, elastoplastic model for the material description, correct definition of the contacts and the existing tolerance among the different system components, reproduction of the preloading stress condition. The present study permitted to define a valid procedure for the realization of numerical models of implant systems.

  10. Contour Detection-Based Realistic Finite-Difference-Time- Domain Models for Microwave Breast Cancer Detection

    Institute of Scientific and Technical Information of China (English)

    王梁; 肖夏; 宋航; 路红; 刘佩芳

    2016-01-01

    In this paper, a collection of three-dimensional(3D)numerical breast models are developed based on clinical magnetic resonance images(MRIs). A hybrid contour detection method is used to create the contour, and the internal space is filled with different breast tissues, with each corresponding to a specified interval of MRI pixel intensity. The developed models anatomically describe the complex tissue structure and dielectric properties in breasts. Besides, they are compatible with finite-difference-time-domain(FDTD)grid cells. Convolutional perfect matched layer(CPML)is applied in conjunction with FDTD to simulate the open boundary outside the model. In the test phase, microwave breast cancer detection simulations are performed in four models with varying radio-graphic densities. Then, confocal algorithm is utilized to reconstruct the tumor images. Imaging results show that the tumor voxels can be recognized in every case, with 2 mm location error in two low density cases and 7 mm─8 mm location errors in two high density cases, demonstrating that the MRI-derived models can characterize the indi-vidual difference between patients’ breasts.

  11. Homogeneous Diffusion Solid Model as a Realistic Approach to Describe Adsorption onto Materials with Different Geometries

    Science.gov (United States)

    Sabio, E.; Zamora, F.; González-García, C. M.; Ledesma, B.; Álvarez-Murillo, A.; Román, S.

    2016-12-01

    In this work, the adsorption kinetics of p-nitrophenol (PNP) onto several commercial activated carbons (ACs) with different textural and geometrical characteristics was studied. For this aim, a homogeneous diffusion solid model (HDSM) was used, which does take the adsorbent shape into account. The HDSM was solved by means of the finite element method (FEM) using the commercial software COMSOL. The different kinetic patterns observed in the experiments carried out can be described by the developed model, which shows that the sharp drop of adsorption rate observed in some samples is caused by the formation of a concentration wave. The model allows one to visualize the changes in concentration taking place in both liquid and solid phases, which enables us to link the kinetic behaviour with the main features of the carbon samples.

  12. The $750$ GeV Diphoton Excesses in a Realistic D-brane Model

    CERN Document Server

    Li, Tianjun; Mayes, Van E; Nanopoulos, Dimitri V

    2016-01-01

    We study the diphoton excesses near $750$ GeV recently reported by the ATLAS and CMS collaborations within the context of a phenomenologically interesting intersecting/magnetized D-brane model on a toroidal orientifold. It is shown that the model contains a SM singlet scalar as well as vector-like quarks and leptons. In addition, it is shown that the singlet scalar has Yukawa couplings with vector-like quarks and leptons such that it may be produced in proton-proton collisions via gluon fusion as well as decay to diphotons through loops involving the vector-like quarks. Moreover, the required vector-like quarks and leptons may appear in complete $SU(5)$ multiplets so that gauge coupling unification may be maintained. Finally, it is shown that the diphoton signal may be explained within the model.

  13. Testing anthropic reasoning for the cosmological constant with a realistic galaxy formation model

    CERN Document Server

    Sudoh, Takahiro; Makiya, Ryu; Nagashima, Masahiro

    2016-01-01

    The anthropic principle is one of the possible explanations for the cosmological constant ($\\Lambda$) problem. In previous studies, a dark halo mass threshold comparable with our Galaxy must be assumed in galaxy formation to get a reasonably large probability of finding the observed small value, $P(<$$\\Lambda_{\\rm obs})$, though stars are found in much smaller galaxies as well. Here we examine the anthropic argument by using a semi-analytic model of cosmological galaxy formation, which can reproduce many observations such as galaxy luminosity functions. We calculate the probability distribution of $\\Lambda$ by running the model code for a wide range of $\\Lambda$, while other cosmological parameters and model parameters for baryonic processes of galaxy formation are kept constant. Assuming that the prior probability distribution is flat per unit $\\Lambda$, and that the number of observers is proportional to stellar mass, we find $P(<$$\\Lambda_{\\rm obs}) = 6.7 \\%$ without introducing any galaxy mass thres...

  14. Realistic D-Brane Models on Warped Throats: Fluxes, Hierarchies and Moduli Stabilization

    CERN Document Server

    Cascales, J F G; Quevedo, Fernando; Uranga, Angel M

    2004-01-01

    We describe the construction of string theory models with semirealistic spectrum in a sector of (anti) D3-branes located at an orbifold singularity at the bottom of a highly warped throat geometry, which is a generalisation of the Klebanov-Strassler deformed conifold. These models realise the Randall-Sundrum proposal to naturally generate the Planck/electroweak hierarchy in a concrete string theory embedding, and yielding interesting chiral open string spectra. We describe examples with Standard Model gauge group (or left-right symmetric extensions) and three families of SM fermions, with correct quantum numbers including hypercharge. The dilaton and complex structure moduli of the geometry are stabilised by the 3-form fluxes required to build the throat. We describe diverse issues concerning the stabilisation of geometric Kahler moduli, like blow-up modes of the orbifold singularities, via D term potentials and gauge theory non-perturbative effects, like gaugino condensation. This local geometry, once embedd...

  15. Can we trust climate models to realistically represent severe European windstorms?

    Science.gov (United States)

    Trzeciak, Tomasz M.; Knippertz, Peter; Pirret, Jennifer S. R.; Williams, Keith D.

    2016-06-01

    Cyclonic windstorms are one of the most important natural hazards for Europe, but robust climate projections of the position and the strength of the North Atlantic storm track are not yet possible, bearing significant risks to European societies and the (re)insurance industry. Previous studies addressing the problem of climate model uncertainty through statistical comparisons of simulations of the current climate with (re-)analysis data show large disagreement between different climate models, different ensemble members of the same model and observed climatologies of intense cyclones. One weakness of such evaluations lies in the difficulty to separate influences of the climate model's basic state from the influence of fast processes on the development of the most intense storms, which could create compensating effects and therefore suggest higher reliability than there really is. This work aims to shed new light into this problem through a cost-effective "seamless" approach of hindcasting 20 historical severe storms with the two global climate models, ECHAM6 and GA4 configuration of the Met Office Unified Model, run in a numerical weather prediction mode using different lead times, and horizontal and vertical resolutions. These runs are then compared to re-analysis data. The main conclusions from this work are: (a) objectively identified cyclone tracks are represented satisfactorily by most hindcasts; (b) sensitivity to vertical resolution is low; (c) cyclone depth is systematically under-predicted for a coarse resolution of T63 by both climate models; (d) no systematic bias is found for the higher resolution of T127 out to about three days, demonstrating that climate models are in fact able to represent the complex dynamics of explosively deepening cyclones well, if given the correct initial conditions; (e) an analysis using a recently developed diagnostic tool based on the surface pressure tendency equation points to too weak diabatic processes, mainly latent

  16. A simple and realistic model system for studying hydrogen bonds in beta-sheets

    DEFF Research Database (Denmark)

    Rossmeisl, Jan; Hinnemann, Berit; Jacobsen, Karsten Wedel

    2003-01-01

    We investigate the interaction between peptide chains at the level of state-of-the-art ab initio density functional theory. We propose an interacting periodic polypeptide model for studying the interactions in beta-sheets and apply this to glycine and alanine peptide chains in both parallel...... and antiparallel structures. The calculated structures of alanine are compared to x-ray structures of beta-sheets and the model is found to reproduce the geometry of the hydrogen bonds very well both concerning parallel and antiparallel beta-sheets. We investigate the structures of both the N-H...O=C and the C...

  17. A more realistic estimate of the variances and systematic errors in spherical harmonic geomagnetic field models

    DEFF Research Database (Denmark)

    Lowes, F.J.; Olsen, Nils

    2004-01-01

    Most modern spherical harmonic geomagnetic models based on satellite data include estimates of the variances of the spherical harmonic coefficients of the model; these estimates are based on the geometry of the data and the fitting functions, and on the magnitude of the residuals. However......, led to quite inaccurate variance estimates. We estimate correction factors which range from 1/4 to 20, with the largest increases being for the zonal, m = 0, and sectorial, m = n, terms. With no correction, the OSVM variances give a mean-square vector field error of prediction over the Earth's surface...

  18. A realistic quasi-physical model of the 100 metre dash

    CERN Document Server

    Mureika, J R

    2000-01-01

    A quasi-physical model (having both physical and mathematical roots) of sprint performances is presented, accounting for the influence of drag modification via wind and altitude variations. The race time corrections for both men and women sprinters are discussed, and theoretical estimates for the associated drag areas are presented. The corrections are consistent with constant-wind estimates of previous authors, however those for variable wind are more accentuated for this model. As a practical example, the nullified World Record and 1988 Olympic 100 m race of Ben Johnson is studied, and compared with the present World Record of 9.79 s.

  19. Cosmological and phenomenological implications of Wilsonian matter in realistic superstring derived models

    Energy Technology Data Exchange (ETDEWEB)

    Faraggi, A.E.

    1996-08-01

    Superstring phenomenology aims at achieving two goals. The first is to reproduce the observed physics of the Standard Model. The second is to identify experimental signatures of superstring unification which, if observed, will provide further evidence for the validity of superstring theory. I discuss such potential signatures of superstring unification. I propose that proton lifetime constraints imply that the Standard Model gauge group must be obtained directly at the string level. In this case the unifying gauge group, for example SO(10), is broken to the Standard Model gauge group by ``Wilson lines``. The symmetry breaking by ``Wilson line`` has important implications. It gives rise to exotic massless states which cannot fit into multiplets of the original unifying gauge group. This is an important feature because it results in conservation laws which forbid the interaction of the exotic ``Wilsonian`` states with the Standard Model states. The ``Wilsonian`` matter states then have important phenomenological implications. I discuss two such implications: exotic ``Wilsonian`` states as dark matter candidates and ``Wilsonian`` matter as the messenger sector in gauge mediated dynamical SUSY breaking scenarios.

  20. Why is the $3\\times 3$ neutrino mixing matrix almost unitary in realistic seesaw models?

    CERN Document Server

    Xing, Z; Xing, Zhi-zhong; Zhou, Shun

    2006-01-01

    A simple extension of the standard model is to introduce $n$ heavy right-handed Majorana neutrinos and preserve its $\\rm SU(2)^{}_L \\times U(1)^{}_Y$ gauge symmetry. Diagonalizing the $(3+n) \\times (3+n)$ neutrino mass matrix, we obtain an exact analytical expression for the effective mass matrix of $\

  1. Constraining models of twin peak quasi-periodic oscillations with realistic neutron star equations of state

    CERN Document Server

    Török, Gabriel; Urbanec, Martin; Šrámková, Eva; Adámek, Karel; Urbancová, Gabriela; Pecháček, Tomáš; Bakala, Pavel; Stuchlík, Zdeněk; Horák, Jiří; Juryšek, Jakub

    2016-01-01

    Twin-peak quasi-periodic oscillations (QPOs) are observed in the X-ray power-density spectra of several accreting low-mass neutron star (NS) binaries. In our previous work we have considered several QPO models. We have identified and explored mass-angular-momentum relations implied by individual QPO models for the atoll source 4U 1636-53. In this paper we extend our study and confront QPO models with various NS equations of state (EoS). We start with simplified calculations assuming Kerr background geometry and then present results of detailed calculations considering the influence of NS quadrupole moment (related to rotationally induced NS oblateness) assuming Hartle-Thorne spacetimes. We show that the application of concrete EoS together with a particular QPO model yields a specific mass-angular-momentum relation. However, we demonstrate that the degeneracy in mass and angular momentum can be removed when the NS spin frequency inferred from the X-ray burst observations is considered. We inspect a large set ...

  2. An approach to creating a more realistic working model from a protein data bank entry

    Science.gov (United States)

    Brandon, Christopher J.; Martin, Benjamin P.; McGee, Kelly J.; Stewart, James J. P.; Braun-Sand, Sonja B.

    2015-01-01

    An accurate model of three-dimensional protein structure is important in a variety of fields such as structure-based drug design and mechanistic studies of enzymatic reactions. While the entries in the Protein Data Bank (http://www.pdb.org) provide valuable information about protein structures, a small fraction of the PDB structures were found to contain anomalies not reported in the PDB file. The semiempirical PM7 method in MOPAC2012 was used for identifying anomalously short hydrogen bonds, C–H···O/C–H···N interactions, non-bonding close contacts, and unrealistic covalent bond lengths in recently published Protein Data Bank files. It was also used to generate new structures with these faults removed. When the semiempirical models were compared to those of PDB_REDO (http://www.cmbi.ru.nl/pdb_redo/), the clashscores, as defined by MolProbity (http://molprobity.biochem.duke.edu/), were better in about 50 % of the structures. The semiempirical models also had a lower root-mean-square-deviation value in nearly all cases than those from PDB_REDO, indicative of a better conservation of the tertiary structure. Finally, the semiempirical models were found to have lower clashscores than the initial PDB file in all but one case. Because this approach maintains as much of the original tertiary structure as possible while improving anomalous interactions, it should be useful to theoreticians, experimentalists, and crystallographers investigating the structure and function of proteins. PMID:25605595

  3. Realistic numerical modelling of human head tissue exposure to electromagnetic waves from cellular phones

    Science.gov (United States)

    Scarella, Gilles; Clatz, Olivier; Lanteri, Stéphane; Beaume, Grégory; Oudot, Steve; Pons, Jean-Philippe; Piperno, Sergo; Joly, Patrick; Wiart, Joe

    2006-06-01

    The ever-rising diffusion of cellular phones has brought about an increased concern for the possible consequences of electromagnetic radiation on human health. Possible thermal effects have been investigated, via experimentation or simulation, by several research projects in the last decade. Concerning numerical modeling, the power absorption in a user's head is generally computed using discretized models built from clinical MRI data. The vast majority of such numerical studies have been conducted using Finite Differences Time Domain methods, although strong limitations of their accuracy are due to heterogeneity, poor definition of the detailed structures of head tissues (staircasing effects), etc. In order to propose numerical modeling using Finite Element or Discontinuous Galerkin Time Domain methods, reliable automated tools for the unstructured discretization of human heads are also needed. Results presented in this article aim at filling the gap between human head MRI images and the accurate numerical modeling of wave propagation in biological tissues and its thermal effects. To cite this article: G. Scarella et al., C. R. Physique 7 (2006).

  4. Quenching vs. Quiescence: forming realistic massive ellipticals with a simple starvation model

    Science.gov (United States)

    Gutcke, Thales A.; Macciò, Andrea V.; Dutton, Aaron A.; Stinson, Greg S.

    2017-01-01

    The decrease in star formation (SF) and the morphological change necessary to produce the z = 0 elliptical galaxy population are commonly ascribed to a sudden quenching event, which is able to rid the central galaxy of its cold gas reservoir in a short time. Following this event, the galaxy is able to prevent further SF and stay quiescent via a maintenance mode. We test whether such a quenching event is truly necessary using a simple model of quiescence. In this model, hot gas (all gas above a temperature threshold) in a ˜1012 M⊙ halo mass galaxy at redshift z ˜ 3 is prevented from cooling. The cool gas continues to form stars at a decreasing rate and the galaxy stellar mass, morphology, velocity dispersion and position on the color magnitude diagram (CMD) proceed to evolve. By z = 0, the halo mass has grown to 1013 M⊙ and the galaxy has attained characteristics typical of an observed z = 0 elliptical galaxy. Our model is run in the framework of a cosmological, smooth particle hydrodynamic code which includes SF, early stellar feedback, supernova feedback, metal cooling and metal diffusion. Additionally, we post-process our simulations with a radiative transfer code to create a mock CMD. In contrast to previous assumptions that a pure "fade away" model evolves too slowly to account for the sparsity of galaxies in the "green valley", we demonstrate crossing times of ≲ 1 Gyr. We conclude that no sudden quenching event is necessary to produce such rapid colour transitions.

  5. Transcranial direct current stimulation (tDCS) in a realistic head model.

    Science.gov (United States)

    Sadleir, Rosalind J; Vannorsdall, Tracy D; Schretlen, David J; Gordon, Barry

    2010-07-15

    Distributions of current produced by transcranial direct current stimulation (tDCS) in humans were predicted by a finite-element model representing several individual and collective refinements over prior efforts. A model of the entire human head and brain was made using a finely meshed (1.1x1.1x1.4mm(3) voxel) tissue dataset derived from the MRI data set of a normal human brain. The conductivities of ten tissues were simulated (bone, scalp, blood, CSF, muscle, white matter, gray matter, sclera, fat, and cartilage). We then modeled the effect of placing a "stimulating" electrode with a saline-like conductivity over F3, and a similar "reference" electrode over a right supraorbital (RS) location, as well as the complements of these locations, to compare expectations derived from the simulation with experimental data also using these locations in terms of the presence or absence of subjective and objective effects. The sensitivity of the results to changes in conductivity values were examined by varying white matter conductivity over a factor of ten. Our simulations established that high current densities were found directly under the stimulating and reference electrodes, but values of the same order of magnitude occurred in other structures, and many areas of the brain that might be behaviorally active were also subjected to what may be substantial amounts of current. The modeling also suggests that more targeted stimulations might be achieved by different electrode topologies. Copyright 2010 Elsevier Inc. All rights reserved.

  6. Realistic modeling and analysis of synchronization dynamics in power-grid networks

    Science.gov (United States)

    Nishikawa, Takashi

    2015-03-01

    An imperative condition for the functioning of a power-grid network is that its power generators remain synchronized. Disturbances can prompt desynchronization, which is a process that has been involved in large power outages. In this talk I will first give a comparative review of three leading models of synchronization in power-grid networks. Each of these models can be derived from first principles under a common framework and represents a power grid as a complex network of coupled second-order phase oscillators with both forcing and damping terms. Since these models require dynamical parameters that are unavailable in typical power-grid datasets, I will discuss an approach to estimate these parameters. The models will be used to show that if the network structure is not homogeneous, generators with identical parameters need to be treated as non-identical oscillators in general. For one of the models, which describes the dynamics of coupled generators through a network of effective interactions, I will derive a condition under which the desired synchronous state is stable. This condition gives rise to a methodology to specify parameter assignments that can enhance synchronization of any given network, which I will demonstrate for a selection of both test systems and real power grids. These parameter assignments can be realized through very fast control loops, and this may help devise new control schemes that offer an additional layer of protection, thus contributing to the development of smart grids that can recover from failures in real time. Funded by ISEN, NSF, and LANL LDRD.

  7. STEPS: efficient simulation of stochastic reaction–diffusion models in realistic morphologies

    Directory of Open Access Journals (Sweden)

    Hepburn Iain

    2012-05-01

    Full Text Available Abstract Background Models of cellular molecular systems are built from components such as biochemical reactions (including interactions between ligands and membrane-bound proteins, conformational changes and active and passive transport. A discrete, stochastic description of the kinetics is often essential to capture the behavior of the system accurately. Where spatial effects play a prominent role the complex morphology of cells may have to be represented, along with aspects such as chemical localization and diffusion. This high level of detail makes efficiency a particularly important consideration for software that is designed to simulate such systems. Results We describe STEPS, a stochastic reaction–diffusion simulator developed with an emphasis on simulating biochemical signaling pathways accurately and efficiently. STEPS supports all the above-mentioned features, and well-validated support for SBML allows many existing biochemical models to be imported reliably. Complex boundaries can be represented accurately in externally generated 3D tetrahedral meshes imported by STEPS. The powerful Python interface facilitates model construction and simulation control. STEPS implements the composition and rejection method, a variation of the Gillespie SSA, supporting diffusion between tetrahedral elements within an efficient search and update engine. Additional support for well-mixed conditions and for deterministic model solution is implemented. Solver accuracy is confirmed with an original and extensive validation set consisting of isolated reaction, diffusion and reaction–diffusion systems. Accuracy imposes upper and lower limits on tetrahedron sizes, which are described in detail. By comparing to Smoldyn, we show how the voxel-based approach in STEPS is often faster than particle-based methods, with increasing advantage in larger systems, and by comparing to MesoRD we show the efficiency of the STEPS implementation. Conclusion STEPS simulates

  8. Statistical multi-path exposure method for assessing the whole-body SAR in a heterogeneous human body model in a realistic environment.

    Science.gov (United States)

    Vermeeren, Günter; Joseph, Wout; Martens, Luc

    2013-04-01

    Assessing the whole-body absorption in a human in a realistic environment requires a statistical approach covering all possible exposure situations. This article describes the development of a statistical multi-path exposure method for heterogeneous realistic human body models. The method is applied for the 6-year-old Virtual Family boy (VFB) exposed to the GSM downlink at 950 MHz. It is shown that the whole-body SAR does not differ significantly over the different environments at an operating frequency of 950 MHz. Furthermore, the whole-body SAR in the VFB for multi-path exposure exceeds the whole-body SAR for worst-case single-incident plane wave exposure by 3.6%. Moreover, the ICNIRP reference levels are not conservative with the basic restrictions in 0.3% of the exposure samples for the VFB at the GSM downlink of 950 MHz. The homogeneous spheroid with the dielectric properties of the head suggested by the IEC underestimates the absorption compared to realistic human body models. Moreover, the variation in the whole-body SAR for realistic human body models is larger than for homogeneous spheroid models. This is mainly due to the heterogeneity of the tissues and the irregular shape of the realistic human body model compared to homogeneous spheroid human body models. Copyright © 2012 Wiley Periodicals, Inc.

  9. Realistic Modeling of Interaction of Quiet-Sun Magnetic Fields with the Chromosphere

    Science.gov (United States)

    Kitiashvili, Irina; Kosovichev, Alexander G.; Mansour, Nagi N.; Wray, Alan A.

    2017-08-01

    High-resolution observations and 3D MHD simulations reveal intense interaction between the convection zone dynamics and the solar atmosphere on subarcsecond scales. To investigate processes of the dynamical coupling and energy exchange between the subsurface layers and the chromosphere we perform 3D radiative MHD modeling for a computational domain that includes the upper convection zone and the chromosphere, and investigate the structure and dynamics for different intensity of the photospheric magnetic flux. For comparison with observations, the simulation models have been used to calculate synthetic Stokes profiles of various spectral lines. The results show intense energy exchange through small-scale magnetized vortex tubes rooted below the photosphere, which provide extra heating of the chromosphere, initiate shock waves, and small-scale eruptions.

  10. SAR Computation inside Fetus by RF Coil during MR Imaging Employing Realistic Numerical Pregnant Woman Model

    Science.gov (United States)

    Kikuchi, Satoru; Saito, Kazuyuki; Takahashi, Masaharu; Ito, Koichi; Ikehira, Hiroo

    This paper presents the computational electromagnetic dosimetry inside an anatomically based pregnant woman models exposed to electromagnetic wave during magnetic resonance imaging. The two types of pregnant woman models corresponding to early gestation and 26 weeks gestation were used for this study. The specific absorption rate (SAR) in and around a fetus were calculated by radiated electromagnetic wave from highpass and lowpass birdcage coil. Numerical calculation results showed that high SAR region is observed at the body in the vicinity of gaps of the coil, and is related to concentrated electric field in the gaps of human body such as armpit and thigh. Moreover, it has confirmed that the SAR in the fetus is less than International Electrotechnical Commission limit of 10W/kg, when whole-body average SARs are 2W/kg and 4W/kg, which are the normal operating mode and first level controlled operating mode, respectively.

  11. Testing anthropic reasoning for the cosmological constant with a realistic galaxy formation model

    Science.gov (United States)

    Sudoh, Takahiro; Totani, Tomonori; Makiya, Ryu; Nagashima, Masahiro

    2017-01-01

    The anthropic principle is one of the possible explanations for the cosmological constant (Λ) problem. In previous studies, a dark halo mass threshold comparable with our Galaxy must be assumed in galaxy formation to get a reasonably large probability of finding the observed small value, P(running the model code for a wide range of Λ, while other cosmological parameters and model parameters for baryonic processes of galaxy formation are kept constant. Assuming that the prior probability distribution is flat per unit Λ, and that the number of observers is proportional to stellar mass, we find P(extremely small, we conclude that the anthropic argument is a viable explanation, if the value of Λ observed in our Universe is determined by a probability distribution.

  12. Neutrino Textures in the Light of Super-Kamiokande Data and a Realistic String Model

    CERN Document Server

    Ellis, Jonathan Richard; Lola, S; Nanopoulos, Dimitri V

    1999-01-01

    Motivated by the Super-Kamiokande atmospheric neutrino data, we discuss possible textures for Majorana and Dirac neutrino masses within the see-saw framework. The main purposes of this paper are twofold: first to obtain intuition from a purely phenomenological analysis, and secondly to explore to what extent it may be realized in a specific model. We comment initially on the simplified two-generation case, emphasizing that large mixing is not incompatible with a large hierarchy of mass eigenvalues. We also emphasize that renormalization-group effects may amplify neutrino mixing, presenting semi-analytic expressions for estimating this amplification. Several examples are then given of three-family neutrino mass textures which may also accommodate the persistent solar neutrino deficit, with different assumptions for the neutrino Dirac mass matrices. We comment on a few features of neutrino mass textures arising in models with a U(1) flavour symmetry. Finally, we discuss the possible pattern of neutrino masses i...

  13. A microscopic "social norm" model to obtain realistic macroscopic velocity and density pedestrian distributions.

    Directory of Open Access Journals (Sweden)

    Francesco Zanlungo

    Full Text Available We propose a way to introduce in microscopic pedestrian models a "social norm" in collision avoiding and overtaking, i.e. the tendency, shared by pedestrians belonging to the same culture, to avoid collisions and perform overtaking in a preferred direction. The "social norm" is implemented, regardless of the specific collision avoiding model, as a rotation in the perceived velocity vector of the opponent at the moment of computation of the collision avoiding strategy, and justified as an expectation that the opponent will follow the same "social norm" (for example a tendency to avoid on the left and overtake on the right, as proposed in this work for Japanese pedestrians. By comparing with real world data, we show that the introduction of this norm allows for a better reproduction of macroscopic pedestrian density and velocity patterns.

  14. A Realistic Cosmological Model Based on Observations and Some Theory Developed Over the Last 90 Years

    CERN Document Server

    Burbidge, Geoffrey

    2008-01-01

    This meeting is entitled "A Century of Cosmology." But most of the papers being given here are based on work done very recently and there is really no attempt being made to critically review what has taken place in the last 90 or 100 years. Instead, in general the participants accept without question that cosmology equates to "hot big bang cosmology" with all of its bells and whistles. All of the theory and the results obtained from observations are interpreted on the assumption that this extremely popular model is the correct one, and observers feel that they have to interpret its results in terms of what this theory allows. No one is attempting to seriously test the model with a view to accepting it or ruling it out. They are aware, as are the theorists, that there are enough free parameters available to fix up almost any model of the type. The current scheme given in detail for example by Spergel et al (206, 2007) demonstrates this. How we got to this stage is never discussed, and little or no attention is...

  15. Photo Realistic 3d Modeling with Uav: GEDİK Ahmet Pasha Mosque in AFYONKARAHİSAR

    Science.gov (United States)

    Uysal, M.; Toprak, A. S.; Polat, N.

    2013-07-01

    Many of the cultural heritages in the world have been totally or partly destroyed by natural events and human activities such as earthquake, flood and fire until the present day. Cultural heritages are legacy for us as well; it is also a fiduciary for next generation. To deliver this fiduciary to the future generations, cultural heritages have to be protected and registered. There are different methods for applying this registry but Photogrammetry is the most accurate and rapid method. Photogrammetry enables us to registry cultural heritages and generating 3D photo-realistic models. Nowadays, 3D models are being used in various fields such as education and tourism. In registration of complex and high construction by Photogrammetry, there are some problems in data acquisition and processing. Especially for high construction's photographs, some additional equipment is required such as balloon and lifter. In recent years The Unmanned Aerial Vehicles (UAV) are commonly started to be used in different fields for different goals. In Photogrammetry, The UAVs are being used for particularly data acquisition. It is not always easy to capture data due to the situation of historical places and their neighbourhood. The use of UAVs for documentation of cultural heritage will make an important contribution. The main goals of this study are to survey cultural heritages by Photogrammetry and to investigate the potential of UAVs in 3D modelling. In this purpose we surveyed Gedik Ahmet Pasha Mosque photogrammetricly by UAV and will produce photorealistic 3D model. Gedik Ahmet Pasha, The Grand Vizier of Fatih Sultan Mehmet, has been in Afyonkarahisar during the campaign to Karaman between the years of 1472-1473. He wanted Architect Ayaz Agha to build a complex of Bathhouse, Mosque and a Madrasah here, Afyon, due to admiration of this city. Gedik Ahmet Pasha Mosque is in the centre of this complex. Gedik Ahmet Pasha Mosque is popularly known as Imaret Mosque among the people of Afyon

  16. Assessment of radiation dose in nuclear cardiovascular imaging using realistic computational models

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Tianwu [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva 4 CH-1211 (Switzerland); Lee, Choonsik [Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institute of Health, Bethesda, Maryland 20852 (United States); Bolch, Wesley E. [Departments of Nuclear and Radiological and Biomedical Engineering, University of Florida, Gainesville, Florida 32611 (United States); Zaidi, Habib, E-mail: habib.zaidi@hcuge.ch [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva 4 CH-1211 (Switzerland); Geneva Neuroscience Center, Geneva University, Geneva CH-1205 (Switzerland); Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen 9700 RB (Netherlands)

    2015-06-15

    Purpose: Nuclear cardiology plays an important role in clinical assessment and has enormous impact on the management of a variety of cardiovascular diseases. Pediatric patients at different age groups are exposed to a spectrum of radiation dose levels and associated cancer risks different from those of adults in diagnostic nuclear medicine procedures. Therefore, comprehensive radiation dosimetry evaluations for commonly used myocardial perfusion imaging (MPI) and viability radiotracers in target population (children and adults) at different age groups are highly desired. Methods: Using Monte Carlo calculations and biological effects of ionizing radiation VII model, we calculate the S-values for a number of radionuclides (Tl-201, Tc-99m, I-123, C-11, N-13, O-15, F-18, and Rb-82) and estimate the absorbed dose and effective dose for 12 MPI radiotracers in computational models including the newborn, 1-, 5-, 10-, 15-yr-old, and adult male and female computational phantoms. Results: For most organs, {sup 201}Tl produces the highest absorbed dose whereas {sup 82}Rb and {sup 15}O-water produce the lowest absorbed dose. For the newborn baby and adult patient, the effective dose of {sup 82}Rb is 48% and 77% lower than that of {sup 99m}Tc-tetrofosmin (rest), respectively. Conclusions: {sup 82}Rb results in lower effective dose in adults compared to {sup 99m}Tc-labeled tracers. However, this advantage is less apparent in children. The produced dosimetric databases for various radiotracers used in cardiovascular imaging, using new generation of computational models, can be used for risk-benefit assessment of a spectrum of patient population in clinical nuclear cardiology practice.

  17. A Computational, Tissue-Realistic Model of Pressure Ulcer Formation in Individuals with Spinal Cord Injury.

    Directory of Open Access Journals (Sweden)

    Cordelia Ziraldo

    2015-06-01

    Full Text Available People with spinal cord injury (SCI are predisposed to pressure ulcers (PU. PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM of ischemia/reperfusion-induced inflammation and PU (the PUABM was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to "better" vs. "worse" outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU.

  18. A Computational, Tissue-Realistic Model of Pressure Ulcer Formation in Individuals with Spinal Cord Injury.

    Science.gov (United States)

    Ziraldo, Cordelia; Solovyev, Alexey; Allegretti, Ana; Krishnan, Shilpa; Henzel, M Kristi; Sowa, Gwendolyn A; Brienza, David; An, Gary; Mi, Qi; Vodovotz, Yoram

    2015-06-01

    People with spinal cord injury (SCI) are predisposed to pressure ulcers (PU). PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM) of ischemia/reperfusion-induced inflammation and PU (the PUABM) was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to "better" vs. "worse" outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs) suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU.

  19. Parallel Solver for Diffuse Optical Tomography on Realistic Head Models with Scattering and Clear Regions.

    Science.gov (United States)

    Placati, Silvio; Guermandi, Marco; Samore, Andrea; Franchi Scarselli, Eleonora; Guerrieri, Roberto

    2015-11-26

    Diffuse Optical Tomography is an imaging technique based on evaluating how light propagates within the human head to obtain functional information about the brain. Precision in reconstructing such an optical properties map is highly affected by the accuracy of the light propagation model implemented, which needs to take into account the presence of clear and scattering tissues. We present a numerical solver based on the radiosity-diffusion model integrating the anatomical information provided by a structural MRI. The solver is designed to run on parallel heterogeneous platforms based on multiple GPUs and CPUs. We demonstrate how the solver provides a 7x speed-up over an isotropic-scattered parallel Monte Carlo engine based on a Radiative Transport Equation for a domain composed of 2 millions voxels, along with a significant improvement in accuracy. The speed-up greatly increases for larger domains, allowing us to compute the light distribution of a full human head ( 3 million voxels) in 116 seconds for the platform used.

  20. Accuracy details in realistic CFD modeling of an industrial centrifugal pump in direct and reverse modes

    Science.gov (United States)

    Páscoa, J. C.; Silva, F. J.; Pinheiro, J. S.; Martins, D. J.

    2010-12-01

    Numerical computation of the flowfield inside a pump is herein used as a numerical laboratory, subject to the limitations of modeling assumptions and to experimental verification. A numerical computation of the flow inside a real industrial centrifugal pump is performed that includes a very sophisticated geometry. Conversely to other computations, in this test case no simplification of the geometry was introduced. Numerical computations are obtained using Spalart-Allmaras turbulence model. A detailed analysis of the turbulent flowstructure is performed for the design point and two off design conditions. Additional computations were performed in order to compare the numerical and experimental pump characteristics; these were obtained under normalized testing conditions. Further computations are presented for the pump working in reverse turbine mode (PAT). Detailed analyses of the flow allow a comparison of the internal flow losses when the pump is operating in direct and reverse mode. This is also useful to help in the selection of an adequate pump geometry that can work in both modes with best efficiency.

  1. A Computational, Tissue-Realistic Model of Pressure Ulcer Formation in Individuals with Spinal Cord Injury

    Science.gov (United States)

    Ziraldo, Cordelia; Solovyev, Alexey; Allegretti, Ana; Krishnan, Shilpa; Henzel, M. Kristi; Sowa, Gwendolyn A.; Brienza, David; An, Gary; Mi, Qi; Vodovotz, Yoram

    2015-01-01

    People with spinal cord injury (SCI) are predisposed to pressure ulcers (PU). PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM) of ischemia/reperfusion-induced inflammation and PU (the PUABM) was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to “better” vs. “worse” outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs) suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU. PMID:26111346

  2. A realistic model for Dark Matter interactions in the neutrino portal paradigm

    CERN Document Server

    González-Macías, Vannia; Wudka, José

    2016-01-01

    We discuss a simple extension of the Standard Model (SM) that provides an explicit realization of the dark-matter (DM) neutrino-portal paradigm. The dark sector is composed of a scalar $ \\Phi $ and a Dirac fermion $ \\Psi $, with the latter assumed to be lighter than the former. These particles interact with the SM through the exchange of a set of heavy Dirac fermion mediators that are neutral under all local SM symmetries, and also under the dark-sector symmetry that stabilizes the $ \\Psi $ against decay. We show that this model can accommodate all experimental and observational constraints provided the DM mass is below $\\sim 35\\, \\gev $ or is in a resonant region of the Higgs or $Z$ boson. We also show that if the dark scalar and dark fermion are almost degenerate in mass, heavier DM fermions are not excluded. We note that in this scenario DM annihilation in the cores of astrophysical objects and the galactic halo produces a monochromatic neutrino beam of energy $ \\mfe $, which provides a clear signature for...

  3. CFD Modelling of Abdominal Aortic Aneurysm on Hemodynamic Loads Using a Realistic Geometry with CT

    Directory of Open Access Journals (Sweden)

    Eduardo Soudah

    2013-01-01

    Full Text Available The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA geometric parameters, wall stress shear (WSS, abdominal flow patterns, intraluminal thrombus (ILT, and AAA arterial wall rupture using computational fluid dynamics (CFD. Real AAA 3D models were created by three-dimensional (3D reconstruction of in vivo acquired computed tomography (CT images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetrahedral aspect ratio for the whole domain. In order to quantify the WSS and the recirculation inside the AAA, a 3D CFD using finite elements analysis was used. The CFD computation was performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with a density of 1050 kg/m3 and a kinematic viscosity of 4×10-3 Pa·s. Parallelization procedures were used in order to increase the performance of the CFD calculations. A relation between AAA geometric parameters (asymmetry index (β, saccular index (γ, deformation diameter ratio (χ, and tortuosity index (ε and hemodynamic loads was observed, and it could be used as a potential predictor of AAA arterial wall rupture and potential ILT formation.

  4. Gravity wave propagation in the realistic atmosphere based on a three-dimensional transfer function model

    Directory of Open Access Journals (Sweden)

    L. Sun

    2007-10-01

    Full Text Available In order to study the filter effect of the background winds on the propagation of gravity waves, a three-dimensional transfer function model is developed on the basis of the complex dispersion relation of internal gravity waves in a stratified dissipative atmosphere with background winds. Our model has successfully represented the main results of the ray tracing method, e.g. the trend of the gravity waves to travel in the anti-windward direction. Furthermore, some interesting characteristics are manifest as follows: (1 The method provides the distribution characteristic of whole wave fields which propagate in the way of the distorted concentric circles at the same altitude under the control of the winds. (2 Through analyzing the frequency and wave number response curve of the transfer function, we find that the gravity waves in a wave band of about 15–30 min periods and of about 200–400 km horizontal wave lengths are most likely to propagate to the 300-km ionospheric height. Furthermore, there is an obvious frequency deviation for gravity waves propagating with winds in the frequency domain. The maximum power of the transfer function with background winds is smaller than that without background winds. (3 The atmospheric winds may act as a directional filter that will permit gravity wave packets propagating against the winds to reach the ionospheric height with minimum energy loss.

  5. Development of a realistic photonic modeling for the evaluation of infrared reflections in the metallic environment of ITER.

    Science.gov (United States)

    Aumeunier, M-H; Travere, J-M

    2010-10-01

    In nuclear fusion experiments, the plasma facing components are exposed to high heat fluxes and infrared (IR) imaging diagnostics are routinely used for surveying their surface temperature for preventing damages. However the future use of metallic components in the ITER tokamak adds complications in temperature estimation. Indeed, low and variable emissivity of the observed surface and the multiple reflections of the light coming from hot regions will have to be understood and then taken into account. In this paper, a realistic photonic modeling based on Monte Carlo ray-tracing codes is used to predict the global response of the complete IR survey system. This also includes the complex vessel geometry and the thermal and optical surface properties using the bidirectional reflectivity distribution function that models the photon-material interactions. The first results of this simulation applied to a reference torus are presented and are used as a benchmark to investigate the validity of the global model. Finally the most critical key model parameters in the reflected signals are identified and their contribution is discussed.

  6. Modelling effects of diquat under realistic exposure patterns in genetically differentiated populations of the gastropod Lymnaea stagnalis.

    Science.gov (United States)

    Ducrot, Virginie; Péry, Alexandre R R; Lagadic, Laurent

    2010-11-12

    Pesticide use leads to complex exposure and response patterns in non-target aquatic species, so that the analysis of data from standard toxicity tests may result in unrealistic risk forecasts. Developing models that are able to capture such complexity from toxicity test data is thus a crucial issue for pesticide risk assessment. In this study, freshwater snails from two genetically differentiated populations of Lymnaea stagnalis were exposed to repeated acute applications of environmentally realistic concentrations of the herbicide diquat, from the embryo to the adult stage. Hatching rate, embryonic development duration, juvenile mortality, feeding rate and age at first spawning were investigated during both exposure and recovery periods. Effects of diquat on mortality were analysed using a threshold hazard model accounting for time-varying herbicide concentrations. All endpoints were significantly impaired at diquat environmental concentrations in both populations. Snail evolutionary history had no significant impact on their sensitivity and responsiveness to diquat, whereas food acted as a modulating factor of toxicant-induced mortality. The time course of effects was adequately described by the model, which thus appears suitable to analyse long-term effects of complex exposure patterns based upon full life cycle experiment data. Obtained model outputs (e.g. no-effect concentrations) could be directly used for chemical risk assessment.

  7. A quantum-classical approach to the molecular dynamics of butatriene cation with a realistic model Hamiltonian.

    Science.gov (United States)

    Sardar, Subhankar; Paul, Amit Kumar; Mondal, Padmabati; Sarkar, Biplab; Adhikari, Satrajit

    2008-11-14

    We are investigating the molecular dynamics of the butatriene cation after excitation from the ground state (X(2)B(2g)) to the first excited electronic state (A(2)B(2u)) by using the time-dependent discrete variable representation (TDDVR) method. The investigation is being carried out with a realistic 18-mode model Hamiltonian consisting of all the vibrational degrees of freedom of the butatriene molecule. First, we perform the simulation on a basic five mode model, and then by including additional thirteen modes as bath on the basic model. This sequential inclusion of bath modes demonstrates the effect of so called weak modes on the subsystem, where the calculations of energy and population transfer from the basic model to the bath quantify the same effect. The spectral profile obtained by using the TDDVR approach shows reasonably good agreement with the results calculated by the quantum mechanical approach/experimental measurement. It appears that the TDDVR approach for those large systems where quantum mechanical description is needed in a restricted region, is a good compromise between accuracy and speed.

  8. 3D electron density distributions in the solar corona during solar minima: assessment for more realistic solar wind modeling

    CERN Document Server

    de Patoul, Judith; Riley, Pete

    2015-01-01

    Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996-1997 and 2008-2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models are more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar regions, and we find that the density in tomographic and thermodynamic solutions varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the...

  9. A battery model that enables consideration of realistic anisotropic environment surrounding an active material particle and its application

    Science.gov (United States)

    Lin, Xianke; Lu, Wei

    2017-07-01

    This paper proposes a model that enables consideration of the realistic anisotropic environment surrounding an active material particle by incorporating both diffusion and migration of lithium ions and electrons in the particle. This model makes it possible to quantitatively evaluate effects such as fracture on capacity degradation. In contrast, the conventional model assumes isotropic environment and only considers diffusion in the active particle, which cannot capture the effect of fracture since it would predict results contradictory to experimental observations. With the developed model we have investigated the effects of active material electronic conductivity, particle size, and State of Charge (SOC) swing window when fracture exists. The study shows that the low electronic conductivity of active material has a significant impact on the lithium ion pattern. Fracture increases the resistance for electron transport and therefore reduces lithium intercalation/deintercalation. Particle size plays an important role in lithium ion transport. Smaller particle size is preferable for mitigating capacity loss when fracture happens. The study also shows that operating at high SOC reduces the impact of fracture.

  10. Numerical simulation of micro-particle deposition in a realistic human upper respiratory tract model during transient breathing cycle

    Institute of Scientific and Technical Information of China (English)

    Jian hua Huang; Lian zhong Zhang

    2011-01-01

    An more reliable human upper respiratory tract model that consisted of an oropharynx and four generations of asymmetric tracheo-bronchial (TB) airways has been constructed to investigate the micro-particle deposition pattern and mass distribution in five lobes under steady inspiratory condition in former work by Huang and Zhang (2011 ).In the present work,transient airflow patterns and particle deposition during both inspiratory and expiratory processes were numerically simulated in the realistic human upper respiratory tract model with 14 cartilaginous rings (CRs) in the tracheal tube.The present model was validated under steady inspiratory flow rates by comparing current results with the theoretical models and published experimental data.The transient deposition fraction was found to strongly depend on breathing flow rate and particle diameter but slightly on turbulence intensity.Particles were mainly distributed in the high axial speed zones and traveled basically following the secondary flow.“Hot spots” of deposition were found in the lower portion of mouth cavity and posterior wall of pharynx/larynx during inspiration,but transferred to upper portion of mouth and interior wall of pharynx/larynx during expiration.The deposition fraction in the trachea during expiration was found to be much higher than that during inspiration because of the stronger secondary flow.

  11. A realistic multimodal modeling approach for the evaluation of distributed source analysis: application to sLORETA.

    Science.gov (United States)

    Cosandier-Rimélé, D; Ramantani, G; Zentner, J; Schulze-Bonhage, A; Dümpelmann, M

    2017-07-05

    Electrical source localization (ESL) deriving from scalp EEG and, in recent years, from intracranial EEG (iEEG), is an established method in epilepsy surgery workup. We aimed to validate the distributed ESL derived from scalp EEG and iEEG, particularly regarding the spatial extent of the source, using a realistic epileptic spike activity simulator. ESL was applied to the averaged scalp EEG and iEEG spikes of two patients with drug-resistant structural epilepsy. The ESL results for both patients were used to outline the location and extent of epileptic cortical patches, which served as the basis for designing a spatiotemporal source model. EEG signals for both modalities were then generated for different anatomic locations and spatial extents. ESL was subsequently performed on simulated signals with sLORETA, a commonly used distributed algorithm. ESL accuracy was quantitatively assessed for iEEG and scalp EEG. The source volume was overestimated by sLORETA at both EEG scales, with the error increasing with source size, particularly for iEEG. For larger sources, ESL accuracy drastically decreased, and reconstruction volumes shifted to the center of the head for iEEG, while remaining stable for scalp EEG. Overall, the mislocalization of the reconstructed source was more pronounced for iEEG. We present a novel multiscale framework for the evaluation of distributed ESL, based on realistic multiscale EEG simulations. Our findings support that reconstruction results for scalp EEG are often more accurate than for iEEG, owing to the superior 3D coverage of the head. Particularly the iEEG-derived reconstruction results for larger, widespread generators should be treated with caution.

  12. A Realistic Model for Observing Spin-Balanced Fulde-Ferrell Superfluid in Honeycomb Lattices

    Institute of Scientific and Technical Information of China (English)

    Bei-Bing Huang

    2016-01-01

    The combination of spin-orbit coupling (SOC) and in-plane Zeeman field breaks time-reversal and inversion symmetries of Fermi gases and becomes a popular way to produce single plane wave Fulde-Ferrell (FF) superfluid.However,atom loss and heating related to SOC have impeded the successful observation of FF state until now.In this work,we propose the realization of spin-balanced FF superfiuid in a honeycomb lattice without SOC and the Zeeman field.A key ingredient of our scheme is generating complex hopping terms in original honeycomb lattices by periodical driving.In our model the ground state is always the FF state,thus the experimental observation has no need of fine tuning.The other advantages of our scheme are its simplicity and feasibility,and thus may open a new route for observing FF superfluids.

  13. Lazy Updating of hubs can enable more realistic models by speeding up stochastic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Ehlert, Kurt; Loewe, Laurence, E-mail: loewe@wisc.edu [Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, Wisconsin 53715 (United States)

    2014-11-28

    To respect the nature of discrete parts in a system, stochastic simulation algorithms (SSAs) must update for each action (i) all part counts and (ii) each action's probability of occurring next and its timing. This makes it expensive to simulate biological networks with well-connected “hubs” such as ATP that affect many actions. Temperature and volume also affect many actions and may be changed significantly in small steps by the network itself during fever and cell growth, respectively. Such trends matter for evolutionary questions, as cell volume determines doubling times and fever may affect survival, both key traits for biological evolution. Yet simulations often ignore such trends and assume constant environments to avoid many costly probability updates. Such computational convenience precludes analyses of important aspects of evolution. Here we present “Lazy Updating,” an add-on for SSAs designed to reduce the cost of simulating hubs. When a hub changes, Lazy Updating postpones all probability updates for reactions depending on this hub, until a threshold is crossed. Speedup is substantial if most computing time is spent on such updates. We implemented Lazy Updating for the Sorting Direct Method and it is easily integrated into other SSAs such as Gillespie's Direct Method or the Next Reaction Method. Testing on several toy models and a cellular metabolism model showed >10× faster simulations for its use-cases—with a small loss of accuracy. Thus we see Lazy Updating as a valuable tool for some special but important simulation problems that are difficult to address efficiently otherwise.

  14. Normal and Pathological NCAT Image and PhantomData Based onPhysiologically Realistic Left Ventricle Finite-Element Models

    Energy Technology Data Exchange (ETDEWEB)

    Veress, Alexander I.; Segars, W. Paul; Weiss, Jeffrey A.; Tsui,Benjamin M.W.; Gullberg, Grant T.

    2006-08-02

    The 4D NURBS-based Cardiac-Torso (NCAT) phantom, whichprovides a realistic model of the normal human anatomy and cardiac andrespiratory motions, is used in medical imaging research to evaluate andimprove imaging devices and techniques, especially dynamic cardiacapplications. One limitation of the phantom is that it lacks the abilityto accurately simulate altered functions of the heart that result fromcardiac pathologies such as coronary artery disease (CAD). The goal ofthis work was to enhance the 4D NCAT phantom by incorporating aphysiologically based, finite-element (FE) mechanical model of the leftventricle (LV) to simulate both normal and abnormal cardiac motions. Thegeometry of the FE mechanical model was based on gated high-resolutionx-ray multi-slice computed tomography (MSCT) data of a healthy malesubject. The myocardial wall was represented as transversely isotropichyperelastic material, with the fiber angle varying from -90 degrees atthe epicardial surface, through 0 degreesat the mid-wall, to 90 degreesat the endocardial surface. A time varying elastance model was used tosimulate fiber contraction, and physiological intraventricular systolicpressure-time curves were applied to simulate the cardiac motion over theentire cardiac cycle. To demonstrate the ability of the FE mechanicalmodel to accurately simulate the normal cardiac motion as well abnormalmotions indicative of CAD, a normal case and two pathologic cases weresimulated and analyzed. In the first pathologic model, a subendocardialanterior ischemic region was defined. A second model was created with atransmural ischemic region defined in the same location. The FE baseddeformations were incorporated into the 4D NCAT cardiac model through thecontrol points that define the cardiac structures in the phantom whichwere set to move according to the predictions of the mechanical model. Asimulation study was performed using the FE-NCAT combination toinvestigate how the differences in contractile function

  15. Study of switching in spin transition compounds within the mechanoelastic model with realistic parameters.

    Science.gov (United States)

    Enachescu, Cristian; Hauser, Andreas

    2016-07-27

    Here we reproduce the static and dynamical properties of spin-crossover complexes in the framework of the mechanoelastic model applied to triangular lattices. The switching processes between the high-spin and low-spin states are studied by combining the Monte Carlo method with the elastic lattice relaxation. The transition probabilities between the two states take into account intrinsic parameters, the values of which are approximated from experimental quantities (e.g., the energy gap, and the degeneracy ratio from the thermodynamic enthalpy and the entropy difference between the states), and the elastic force or elastic energy stored in the springs connecting the spin-changing centres. The value of the corresponding spring constant is estimated from the experimentally determined variation of the ligand-field strengths in the two spin states due to the cooperativity and the bulk modulus. Both simulated hysteresis loops and relaxation curves are in agreement with experimental data. Cooperativity related phenomena such as like-spin domain formation and the evolution of the interaction distribution with the HS fraction are also analysed.

  16. Application of LES in the study of inlet flow field in marine gas turbine

    Institute of Scientific and Technical Information of China (English)

    SHI Bao-long; SUN Hai-ou; SUN Tao; HU Yan-yong

    2005-01-01

    The structure and aerodynamics performance of gas turbine inlet system is an important part of technology of gas turbine installed on naval vessels. The design and numerical simulations of gas turbine inlet system are conducted and reliable foundation for design and manufacture of marine gas turbine inlet system of high performance is provided. Numerical simulations and experiments of two inlet system models of gas turbine are conducted with satisfactory results and are of significance to the actual application of the inlet system.

  17. The ASTROID Simulator Software Package: Realistic Modelling of High-Precision High-Cadence Space-Based Imaging

    CERN Document Server

    Marcos-Arenal, P; De Ridder, J; Huygen, R; Aerts, C

    2014-01-01

    The preparation of a space-mission that carries out any kind of imaging to detect high-precision low-amplitude variability of its targets requires a robust model for the expected performance of its instruments. This model cannot be derived from simple addition of noise properties due to the complex interaction between the various noise sources. While it is not feasible to build and test a prototype of the imaging device on-ground, realistic numerical simulations in the form of an end-to-end simulator can be used to model the noise propagation in the observations. These simulations not only allow studying the performance of the instrument, its noise source response and its data quality, but also the instrument design verification for different types of configurations, the observing strategy and the scientific feasibility of an observing proposal. In this way, a complete description and assessment of the objectives to expect from the mission can be derived. We present a high-precision simulation software packag...

  18. Realistic Numerical and Analytical Modeling of Light Scattering in Brain Tissue for Optogenetic Applications(1,2,3).

    Science.gov (United States)

    Yona, Guy; Meitav, Nizan; Kahn, Itamar; Shoham, Shy

    2016-01-01

    In recent years, optogenetics has become a central tool in neuroscience research. Estimating the transmission of visible light through brain tissue is of crucial importance for controlling the activation levels of neurons in different depths, designing optical systems, and avoiding lesions from excessive power density. The Kubelka-Munk model and Monte Carlo simulations have previously been used to model light propagation through rodents' brain tissue, however, these prior attempts suffer from fundamental shortcomings. Here, we introduce and study two modified approaches for modeling the distributions of light emanating from a multimode fiber and scattering through tissue, using both realistic numerical Monte Carlo simulations and an analytical approach based on the beam-spread function approach. We demonstrate a good agreement of the new methods' predictions both with recently published data, and with new measurements in mouse brain cortical slices, where our results yield a new cortical scattering length estimate of ∼47 µm at λ = 473 nm, significantly shorter than ordinarily assumed in optogenetic applications.

  19. Magnetic breakdown phenomenon in quasi-two-dimensional organic conductors: A quantum model inspired by a realistic band structure

    Science.gov (United States)

    Kim, Ju H.; Han, S. Y.; Brooks, J. S.

    1999-08-01

    We investigate the phenomenon of magnetic breakdown in quasi-two-dimensional organic conductors such as α-(ET)2KHg(SCN)4 and κ-(ET)2Cu(NCS)2 by constructing a tight-binding model based on a realistic band structure which is derived from the crystallographic data. We solve the model numerically to compute the magnetic field dependence of the magnetization and show that the present model accounts naturally for the experimentally observed magnetization oscillation frequencies that are forbidden in the semiclassical picture. The computed values of the fundamental and magnetic breakdown frequencies with no adjustable parameters are close to the experimentally measured values. For completeness, we carry out the computation for both canonical (fixed number of particles) and grand canonical (fixed chemical potential) ensembles, and show that the forbidden frequencies appear in both cases. Hence, the appearance of anomalous frequencies in the de Haas-van Alphen effect has a quantum-mechanical origin and arises from the interplay of electronic states from two partially occupied bands near the Fermi energy as a function of magnetic field. We also compute the temperature dependence of the magnetization and apply ad hoc the Lifshitz-Kosevich analysis to the amplitudes of the Fourier components at moderately high temperatures. This yields effective mass values for α-(ET)2KHg(SCN)4 in good agreement with experimental values.

  20. Constraints to do realistic modeling of the electric field ahead of the tip of a lightning leader

    Science.gov (United States)

    Skeltved, Alexander Broberg; Østgaard, Nikolai; Mezentsev, Andrew; Lehtinen, Nikolai; Carlson, Brant

    2017-08-01

    Several computer models exist to explain the observation of terrestrial gamma-ray flashes (TGFs). Some of these models estimate the electric field ahead of lightning leaders and its effects on electron acceleration and multiplication. In this paper, we derive a new set of constraints to do more realistic modeling. We determine initial conditions based on in situ measurements of electric field and vertical separation between the main charge layers of thunderclouds. A maximum electric field strength of 50 kV/cm at sea level is introduced as the upper constraint for the leader electric field. The threshold for electron avalanches to develop of 2.86 kV/cm at sea level is introduced as the lower value. With these constraints, we determine a region where acceleration and multiplication of electrons occur. The maximum potential difference in this region is found to be ˜52 MV, and the corresponding number of avalanche multiplication lengths is ˜3.5. We then quantify the effect of the ambient electric field compared to the leader field at the upper altitude of the negative tip. Finally, we argue that only leaders with the highest potential difference between its tips (˜600 MV) can be candidates for the production of TGFs. However, with the assumptions we have used, these cannot explain the observed maximum energies of at least 40 MeV. Open questions with regard to the temporal development of the streamer zone and its effect on the shape of the electric field remain.

  1. A Framework for Realistic Modeling and Display of Object Surface Appearance

    Science.gov (United States)

    Darling, Benjamin A.

    With advances in screen and video hardware technology, the type of content presented on computers has progressed from text and simple shapes to high-resolution photographs, photorealistic renderings, and high-definition video. At the same time, there have been significant advances in the area of content capture, with the development of devices and methods for creating rich digital representations of real-world objects. Unlike photo or video capture, which provide a fixed record of the light in a scene, these new technologies provide information on the underlying properties of the objects, allowing their appearance to be simulated for novel lighting and viewing conditions. These capabilities provide an opportunity to continue the computer display progression, from high-fidelity image presentations to digital surrogates that recreate the experience of directly viewing objects in the real world. In this dissertation, a framework was developed for representing objects with complex color, gloss, and texture properties and displaying them onscreen to appear as if they are part of the real-world environment. At its core, there is a conceptual shift from a traditional image-based display workflow to an object-based one. Instead of presenting the stored patterns of light from a scene, the objective is to reproduce the appearance attributes of a stored object by simulating its dynamic patterns of light for the real viewing and lighting geometry. This is accomplished using a computational approach where the physical light sources are modeled and the observer and display screen are actively tracked. Surface colors are calculated for the real spectral composition of the illumination with a custom multispectral rendering pipeline. In a set of experiments, the accuracy of color and gloss reproduction was evaluated by measuring the screen directly with a spectroradiometer. Gloss reproduction was assessed by comparing gonio measurements of the screen output to measurements of the

  2. Ponce de Leon Inlet, FL: An Integrated Hydrodynamic and Morphologic Assessment of Design Alternatives using the U.S. Army Corps of Engineers’ Coastal Modeling System

    Science.gov (United States)

    2009-07-01

    Ponce de Leon Inlet, FL: An Integrated Hydrodynamic and Morphologic Assessment of Design Alternatives using the U.S. Army Corps of Engineers...DATES COVERED - 4. TITLE AND SUBTITLE Ponce de Leon Inlet, FL: An Integrated Hydrodynamic and Morphologic Assessment of Design Alternatives...SUPPLEMENTARY NOTES 14. ABSTRACT Shoaling and channel migration at Ponce de Leon Inlet, FL, have caused persistently hazardous navigation conditions

  3. Agent-based modeling traction force mediated compaction of cell-populated collagen gels using physically realistic fibril mechanics.

    Science.gov (United States)

    Reinhardt, James W; Gooch, Keith J

    2014-02-01

    Agent-based modeling was used to model collagen fibrils, composed of a string of nodes serially connected by links that act as Hookean springs. Bending mechanics are implemented as torsional springs that act upon each set of three serially connected nodes as a linear function of angular deflection about the central node. These fibrils were evaluated under conditions that simulated axial extension, simple three-point bending and an end-loaded cantilever. The deformation of fibrils under axial loading varied <0.001% from the analytical solution for linearly elastic fibrils. For fibrils between 100 μm and 200 μm in length experiencing small deflections, differences between simulated deflections and their analytical solutions were <1% for fibrils experiencing three-point bending and <7% for fibrils experiencing cantilever bending. When these new rules for fibril mechanics were introduced into a model that allowed for cross-linking of fibrils to form a network and the application of cell traction force, the fibrous network underwent macroscopic compaction and aligned between cells. Further, fibril density increased between cells to a greater extent than that observed macroscopically and appeared similar to matrical tracks that have been observed experimentally in cell-populated collagen gels. This behavior is consistent with observations in previous versions of the model that did not allow for the physically realistic simulation of fibril mechanics. The significance of the torsional spring constant value was then explored to determine its impact on remodeling of the simulated fibrous network. Although a stronger torsional spring constant reduced the degree of quantitative remodeling that occurred, the inclusion of torsional springs in the model was not necessary for the model to reproduce key qualitative aspects of remodeling, indicating that the presence of Hookean springs is essential for this behavior. These results suggest that traction force mediated matrix

  4. Experimental Section: On the magnetic field distribution generated by a dipolar current source situated in a realistically shaped compartment model of the head

    NARCIS (Netherlands)

    Meijs, J.W.H.; Bosch, F.G.C.; Peters, M.J.; Lopes da silva, F.H.

    1987-01-01

    The magnetic field distribution around the head is simulated using a realistically shaped compartment model of the head. The model is based on magnetic resonance images. The 3 compartments describe the brain, the skull and the scalp. The source is represented by a current dipole situated in the

  5. The influence of frontal sinus in brain activation measurements by near-infrared spectroscopy analyzed by realistic head models

    Science.gov (United States)

    Kurihara, Kazuki; Kawaguchi, Hiroshi; Obata, Takayuki; Ito, Hiroshi; Sakatani, Kaoru; Okada, Eiji

    2012-01-01

    Adequate modeling of light propagation in the head is important to predict the sensitivity of NIRS signal and the spatial sensitivity profile of source-detector pairs. The 3D realistic head models of which the geometry is based upon the anatomical images acquired by magnetic resonance imaging and x-ray computed tomography are constructed to investigate the influence of the frontal sinus on the NIRS signal and spatial sensitivity. Light propagation in the head is strongly affected by the presence of the frontal sinus. The light tends to propagate around the frontal sinus. The influence of the frontal sinus on the sensitivity of the NIRS signal to the brain activation is not consistent and depends on the depth of the frontal sinus, the optical properties of the superficial tissues and the relative position between the source-detector pair and the frontal sinus. The frontal sinus located in the shallow region of the skull tends to reduce the sensitivity of the NIRS signal while the deep frontal sinus can increase the sensitivity of the NIRS signal. PMID:23024906

  6. Bending and Twisting the Embryonic Heart: A Computational Model for C-Looping Based on Realistic Geometry

    Directory of Open Access Journals (Sweden)

    Yunfei eShi

    2014-08-01

    Full Text Available The morphogenetic process of cardiac looping transforms the straight heart tube into a curved tube that resembles the shape of the future four-chambered heart. Although great progress has been made in identifying the molecular and genetic factors involved in looping, the physical mechanisms that drive this process have remained poorly understood. Recent work, however, has shed new light on this complicated problem. After briefly reviewing the current state of knowledge, we propose a relatively comprehensive hypothesis for the mechanics of the first phase of looping, termed c-looping, as the straight heart tube deforms into a c-shaped tube. According to this hypothesis, differential hypertrophic growth in the myocardium supplies the main forces that cause the heart tube to bend ventrally, while regional growth and contraction in the omphalomesenteric veins (primitive atria and compressive loads exerted by the splanchnopleuric membrane drive rightward torsion. A computational model based on realistic embryonic heart geometry is used to test this hypothesis. The behavior of the model is in reasonable agreement with available experimental data from control and perturbed embryos, offering support for our hypothesis. The results also suggest, however, that several other mechanisms contribute secondarily to normal looping, and we speculate that these mechanisms play backup roles when looping is perturbed. Finally, some outstanding questions are discussed for future study.

  7. Joint inversion of seismic traveltime and gravity data: A synthetic study using geologically realistic models from the Voisey's Bay deposit

    Science.gov (United States)

    Carter-McAuslan, A.; Lelièvre, P. G.; Farquharson, C.

    2012-12-01

    Seismic methods provide high resolving potential for use in mineral exploration. Unfortunately, complicated hard-rock geology can make seismic data processing and interpretation difficult. It may help to overcome these difficulties by jointly inverting seismic tomography data with gravity data. We investigated the viability of deterministic minimum-structure style joint inversion of seismic traveltime and gravity data for the delineation of geological targets from the Voisey's Bay sulfide deposit in Labrador, Canada. These tests also assessed the potential of employing borehole gravity. A number of synthetic Earth models were created based on the geology of the Eastern Deeps zone of the Voisey's Bay deposit. These models were built on triangular (2D) and tetrahedral (3D) unstructured meshes, allowing for efficient generation of complicated, realistic geological structures. 2D models were based on conceptualized models of the Eastern Deeps. A detailed 3D model was built using information from extensive drilling. Single property and joint inversions were performed with seismic traveltimes and both ground-based and borehole gravity. There is a known relationship between seismic velocity and density for both silicate rocks and sulphide minerals for our study area; this lithological relationship was used to design an appropriate coupling strategy in the joint inversions. Joint inversions were able to successfully locate a buried high contrast target with a variety of survey designs. Experimentation with noise levels, mesh design, and various inversion parameters has lead to a better understanding of how to practically apply joint inversion of traveltimes and gravity data to this and similar exploration problems.

  8. Spiral-Wave Dynamics in Ionically Realistic MathematicalModels for Human Ventricular Tissue: The Effects of PeriodicDeformation

    Directory of Open Access Journals (Sweden)

    Alok Ranjan Nayak

    2014-06-01

    Full Text Available We carry out an extensive numerical study of the dynamics of spiral waves of electrical activation, in the presence of periodic deformation (PD in two-dimensional simulation domains, in the biophysically realistic mathematical models of human ventricular tissue due to (a ten-Tusscher and Panfilov (the TP06 model and (b ten-Tusscher, Noble, Noble, and Panfilov (theTNNP04 model. We first consider simulations in cable-type domains, in which we calculate the conduction velocity $CV$ andthe wavelength $lambda$ of a plane wave; we show that PD leads to a periodic, spatial modulation of $CV$ and a temporallyperiodic modulation of $lambda$; both these modulations depend on the amplitude and frequency of the PD. We then examine three types of initial conditions for both TP06 and TNNP04 models and show that the imposition of PD leads to a rich variety ofspatiotemporal patterns in the transmembrane potential including states with a single rotating spiral (RS wave, a spiral-turbulence (ST state with a single meandering spiral, an ST state with multiple broken spirals, and a state SA in which all spirals are absorbed at the boundaries of our simulation domain. We find, for both TP06 and TNNP04 models, that spiral-wave dynamics depends sensitively on the amplitude and frequency of PD and the initial condition. We examine how these different types of spiral-wave states can be eliminated in the presence of PD by the application of low-amplitude pulses on square and rectangular control meshes. We suggest specific experiments that can test the results of our simulations.

  9. Spiral-wave dynamics in ionically realistic mathematical models for human ventricular tissue: the effects of periodic deformation.

    Science.gov (United States)

    Nayak, Alok R; Pandit, Rahul

    2014-01-01

    We carry out an extensive numerical study of the dynamics of spiral waves of electrical activation, in the presence of periodic deformation (PD) in two-dimensional simulation domains, in the biophysically realistic mathematical models of human ventricular tissue due to (a) ten-Tusscher and Panfilov (the TP06 model) and (b) ten-Tusscher, Noble, Noble, and Panfilov (the TNNP04 model). We first consider simulations in cable-type domains, in which we calculate the conduction velocity θ and the wavelength λ of a plane wave; we show that PD leads to a periodic, spatial modulation of θ and a temporally periodic modulation of λ; both these modulations depend on the amplitude and frequency of the PD. We then examine three types of initial conditions for both TP06 and TNNP04 models and show that the imposition of PD leads to a rich variety of spatiotemporal patterns in the transmembrane potential including states with a single rotating spiral (RS) wave, a spiral-turbulence (ST) state with a single meandering spiral, an ST state with multiple broken spirals, and a state SA in which all spirals are absorbed at the boundaries of our simulation domain. We find, for both TP06 and TNNP04 models, that spiral-wave dynamics depends sensitively on the amplitude and frequency of PD and the initial condition. We examine how these different types of spiral-wave states can be eliminated in the presence of PD by the application of low-amplitude pulses by square- and rectangular-mesh suppression techniques. We suggest specific experiments that can test the results of our simulations.

  10. Numerical modeling of percutaneous auricular vagus nerve stimulation: a realistic 3D model to evaluate sensitivity of neural activation to electrode position.

    Science.gov (United States)

    Samoudi, Amine M; Kampusch, Stefan; Tanghe, Emmeric; Széles, Jozsef C; Martens, Luc; Kaniusas, Eugenijus; Joseph, Wout

    2017-02-13

    Percutaneous stimulation of the auricular branch of the vagus nerve (pVNS) by miniaturized needle electrodes in the auricle gained importance as a treatment for acute and chronic pain. The objective is to establish a realistic numerical model of pVNS and investigate the effects of stimulation waveform, electrodes' depth, and electrodes' position on nerve excitation threshold and the percentage of stimulated nerves. Simulations were performed with Sim4Life. An electrostatic solver and neural tissue models were combined for electromagnetic and neural simulation. The numerical model consisted of a realistic high-resolution model of a human ear, blood vessels, nerves, and three needle electrodes. A novel 3D ear model was established, including blood vessels and nerves. The electric field distribution was extracted and evaluated. Maximum sensitivity to needles' depth and displacement was evaluated to be 9.8 and 15.5% per 0.1 mm, respectively. Stimulation was most effective using biphasic compared to mono-phasic pulses. The established model allows easy and quantitative evaluation of various stimulation setups, enabling optimization of pVNS in experimental settings. Results suggest a high sensitivity of pVNS to the electrodes' position and depth, implying the need for precise electrode positioning. Validation of the model needs to be performed.

  11. Hemodynamic Changes Caused by Flow Diverters in Rabbit Aneurysm Models: Comparison of Virtual and Realistic FD Deployments Based on Micro-CT Reconstruction.

    Science.gov (United States)

    Xu, Jinyu; Deng, Benqiang; Fang, Yibin; Yu, Ying; Cheng, Jiyong; Wang, Shengzhang; Wang, Kuizhong; Liu, Jian-Min; Huang, Qinghai

    2013-01-01

    Adjusting hemodynamics via flow diverter (FD) implantation is emerging as a novel method of treating cerebral aneurysms. However, most previous FD-related hemodynamic studies were based on virtual FD deployment, which may produce different hemodynamic outcomes than realistic (in vivo) FD deployment. We compared hemodynamics between virtual FD and realistic FD deployments in rabbit aneurysm models using computational fluid dynamics (CFD) simulations. FDs were implanted for aneurysms in 14 rabbits. Vascular models based on rabbit-specific angiograms were reconstructed for CFD studies. Real FD configurations were reconstructed based on micro-CT scans after sacrifice, while virtual FD configurations were constructed with SolidWorks software. Hemodynamic parameters before and after FD deployment were analyzed. According to the metal coverage (MC) of implanted FDs calculated based on micro-CT reconstruction, 14 rabbits were divided into two groups (A, MC >35%; B, MC 0.05). The normalized mean WSS in Group A after realistic FD implantation was significantly lower than that of Group B. All parameters in Group B exhibited no significant difference between realistic and virtual FDs. This study confirmed MC-correlated differences in hemodynamic parameters between realistic and virtual FD deployment.

  12. Morphodynamics of tidal inlets in a tropical monsoon area

    NARCIS (Netherlands)

    Lam, N.T.; Stive, M.J.F.; Verhagen, H.J.; Wang, Z.B.

    2007-01-01

    Morphodynamics of a tidal inlet system on a micro-tidal coast in a tropical monsoon influenced region is modelled and discussed. Influences of river flow and wave climate on the inlet morphology are investigated with the aid of process-based state-of-the-art numerical models. Seasonal and episodic b

  13. CFD numerical simulation of Archimedes spiral inlet hydrocyclone

    Science.gov (United States)

    Zhang, L.; Wei, L.; Chang, B. H.; Xing, J. L.; Jia, K.

    2013-12-01

    For traditional linear type inlet, hydrocyclone has an unstable inner field, high turbulence intensity and low separation efficiency, this paper proposes an inlet mode that uses an Archimedes spiral hydrocyclone. A Mixture liquid-solid multiphase flow model combined with the kinetic theory of granular flow was used to simulate the high concentration water-sand-air three-phase flow in a hydrocyclone. We analyzed the pressure field, velocity field and turbulent kinetic energy and compared with traditional linear type inlet hydrocyclone inner field. The results show that Archimedes spiral inlet hydrocyclone's pressure field is evenly distributed. The Archimedes spiral inlet hydrocyclone can guide and accelerate the mixture flow and produce small forced vortex and less short circuit flow. The particles easily go to the outer vortex and are separated. The Archimedes spiral inlet hydrocyclone has effectively improved the stability of inner flow field and separation efficiency.

  14. New River Inlet DRI: Observations and Modeling of Flow and Material Exchange & Field and Numerical Study of the Columbia River Mouth

    Science.gov (United States)

    2013-09-30

    inlet affecting salinity and temperature variations and associated acoustic properties. The geometric confirguration of the New River Inlet estuary and...Thornton (2012) Frequency-Wavenumber Velocity Spectra, Taylor’s Hypothesis and Length-Scales in a Natural Gravel -Bed River, Water Resources Research

  15. Creation of a realistic model for removal of a metallic corneal foreign body for less than $75.

    Directory of Open Access Journals (Sweden)

    Sayegh, Julie Sami

    2017-01-01

    Full Text Available Metallic corneal foreign bodies (MCFBs are one of the most common causes of ocular injury presenting to the emergency department. Delays in removal, or forceful attempts to remove the MCFB can lead to infection, further injury to the eye, and worsening of vision. In order to prevent these underlying complications, it is imperative for the medical provider to properly master this technique. As current trends in simulation become more focused on patient safety, task-trainers can provide an invaluable learning experience for residents, medical students and physicians. Models made from bovine eyes, agar plates, gelatin, and corneas created from glass and paraffin wax have been previously been created.One study also used a rubber glove filled with water to simulate intraocular measurement with a Tonopen. However the use of corneas created from ballistics gel for MCFB removal and intraocular pressure measurement has not been studied. We propose a realistic, sustainable, cost-effective MCFB task-trainer to introduce the fundamental skills required for MCFB removal and measurement of intraocular pressure with a Tonopen. A pilot survey study performed on medical students and emergency medicine resident physicians showed an increase in comfort levels performing both MCFB removal and measurement of intraocular pressure with a Tonopen after using this task-trainer.

  16. Effects of Flow Parameters and Inlet Geometry on Cyclone Efficiency

    Institute of Scientific and Technical Information of China (English)

    赵兵涛

    2006-01-01

    A novel cyclone design, named converging symmetrical spiral inlet (CSSI) cyclone, is developed by improving the inlet geometry of conventional tangential single inlet (CTSI) cyclone for enhancing the physical performance of the cyclone.The collection efficiency of the CSSI cyclone is experimentally compared with the widely used CTSI cyclone. The results indicate that the CSSI cyclone provides higher collection efficiency by 5%~20% than that of the CTSI cyclone for a tested inlet velocity range of 11.99~23.85 m/s. In addition, the results of collection efficiency comparison between experimental data and theoretical model are also discussed.

  17. Inlet and airframe compatibility for a V/STOL fighter/attack aircraft with top-mounted inlets

    Science.gov (United States)

    Durston, D. A.; Smeltzer, D. B.

    1982-01-01

    Aerodynamic force and inlet pressure data are obtained for 9.5% force and pressure models of a V/STOL fighter/attack aircraft configuration with top mounted twin inlets. Data are presented from tests conducted in the Ames Unitary Wind Tunnels at Mach numbers of 0.6, 0.9, and 1.2 at angles of attack up to 27 deg. and angles of sideslip up to 12 deg. Trimmed aerodynamic characteristics and inlet performance are compared for three different leading edge extension (LEX) configurations. The effects of wing leading and trailing-edge flaps on the inlet are also determined. Maneuver perfromance is calculated form combined force and inlet pressure data. The largest of the three LEX sizes tested gives the best airplane maneuver performance. Wing flap deflections improved inlet recovery at all Mach numbers.

  18. Modeling the Normal and Neoplastic Cell Cycle with 'Realistic Boolean Genetic Networks': Their Application for Understanding Carcinogenesis and Assessing Therapeutic Strategies

    Science.gov (United States)

    Szallasi, Zoltan; Liang, Shoudan

    2000-01-01

    In this paper we show how Boolean genetic networks could be used to address complex problems in cancer biology. First, we describe a general strategy to generate Boolean genetic networks that incorporate all relevant biochemical and physiological parameters and cover all of their regulatory interactions in a deterministic manner. Second, we introduce 'realistic Boolean genetic networks' that produce time series measurements very similar to those detected in actual biological systems. Third, we outline a series of essential questions related to cancer biology and cancer therapy that could be addressed by the use of 'realistic Boolean genetic network' modeling.

  19. Automatic recognition of equipment and components photo realistic 3D models; Reconocimiento automatico de equipos y componentes en modelos fotorrealistas 3D

    Energy Technology Data Exchange (ETDEWEB)

    Sarti Fernandez, F.

    2014-07-01

    Laser scanner technology, through the photo-realistic models, has demonstrated for years its great utility to achieve objectives of optimization of the maintenance work, by the advantage presented by allowing remote access to the work environment, prior to performing these tasks. (Author)

  20. The effects of a realistic hollow cathode plasma contactor model on the simulation of bare electrodynamic tether systems

    Science.gov (United States)

    Blash, Derek M.

    The region known as Low-Earth Orbit (LEO) has become populated with artificial satellites and space debris since humanities initial venture into the region. This has turned LEO into a hazardous region. Since LEO is very valuable to many different countries, there has been a push to prevent further buildup and talk of even deorbiting spent satellites and debris already in LEO. One of the more attractive concepts available for deorbiting debris and spent satellites is a Bare Electrodynamic Tether (BET). A BET is a propellantless propulsion technique in which two objects are joined together by a thin conducting material. When these tethered objects are placed in LEO, the tether sweeps across the magnetic field lines of the Earth and induces an electromotive force (emf) along the tether. Current from the space plasma is collected on the bare tether under the action of the induced emf, and this current interacts with the Earth's magnetic field to create a drag force that can be used to deorbit spent satellites and space debris. A Plasma Contactor (PC) is used to close the electrical circuit between the BET and the ionospheric plasma. The PC requires a voltage and, depending on the device, a gas flow to emit electrons through a plasma bridge to the ionospheric plasma. The PC also can require a plasma discharge electrode and a heater to condition the PC for operation. These parameters as well as the PC performance are required to build an accurate simulation of a PC and, therefore, a BET deorbiting system. This thesis focuses on the development, validation, and implementation of a simulation tool to model the effects of a realistic hollow cathode PC system model on a BET deorbit system.

  1. Inlet Geomorphology Evolution Work Unit

    Science.gov (United States)

    2015-10-30

    the expected behavior and benefits of nearshore placement. Nearshore placement studies have been documented in two journal papers, one technical...Coastal Inlets Research Program Inlet Geomorphology Evolution Work Unit The Inlet Geomorphology Evolution work unit of the CIRP develops methods...sensing measurements, and USACE projects to create valuable guidance that address geomorphic questions. The present focus of the work unit is a common

  2. Learning from Nature - Mapping of Complex Hydrological and Geomorphological Process Systems for More Realistic Modelling of Hazard-related Maps

    Science.gov (United States)

    Chifflard, Peter; Tilch, Nils

    2010-05-01

    Introduction Hydrological or geomorphological processes in nature are often very diverse and complex. This is partly due to the regional characteristics which vary over time and space, as well as changeable process-initiating and -controlling factors. Despite being aware of this complexity, such aspects are usually neglected in the modelling of hazard-related maps due to several reasons. But particularly when it comes to creating more realistic maps, this would be an essential component to consider. The first important step towards solving this problem would be to collect data relating to regional conditions which vary over time and geographical location, along with indicators of complex processes. Data should be acquired promptly during and after events, and subsequently digitally combined and analysed. Study area In June 2009, considerable damage occurred in the residential area of Klingfurth (Lower Austria) as a result of great pre-event wetness and repeatedly heavy rainfall, leading to flooding, debris flow deposit and gravitational mass movement. One of the causes is the fact that the meso-scale watershed (16 km²) of the Klingfurth stream is characterised by adverse geological and hydrological conditions. Additionally, the river system network with its discharge concentration within the residential zone contributes considerably to flooding, particularly during excessive rainfall across the entire region, as the flood peaks from different parts of the catchment area are superposed. First results of mapping Hydro(geo)logical surveys across the entire catchment area have shown that - over 600 gravitational mass movements of various type and stage have occurred. 516 of those have acted as a bed load source, while 325 mass movements had not reached the final stage yet and could thus supply bed load in the future. It should be noted that large mass movements in the initial or intermediate stage were predominately found in clayey-silty areas and weathered material

  3. Cardiac autonomic functions and the emergence of violence in a highly realistic model of social conflict in humans.

    Directory of Open Access Journals (Sweden)

    Jozsef eHaller

    2014-10-01

    Full Text Available Among the multitude of factors that can transform human social interactions into violent conflicts, biological features received much attention in recent years as correlates of decision making and aggressiveness especially in critical situations. We present here a highly realistic new model of human aggression and violence, where genuine acts of aggression are readily performed and which at the same time allows the parallel recording of biological concomitants. Particularly, we studied police officers trained at the International Training Centre (Budapest, Hungary, who are prepared to perform operations under extreme conditions of stress. We found that aggressive arousal can transform a basically peaceful social encounter into a violent conflict. Autonomic recordings show that this change is accompanied by increased heart rates, which was associated earlier with reduced cognitive complexity of perceptions (attentional myopia and promotes a bias towards hostile attributions and aggression. We also observed reduced heart rate variability in violent subjects, which is believed to signal a poor functioning of prefrontal-subcortical inhibitory circuits and reduces self-control. Importantly, these autonomic particularities were observed already at the beginning of social encounters i.e. before aggressive acts were initiated, suggesting that individual characteristics of the stress-response define the way in which social pressure affects social behavior, particularly the way in which this develops into violence. Taken together, these findings suggest that cardiac autonomic functions are valuable external symptoms of internal motivational states and decision making processes, and raise the possibility that behavior under social pressure can be predicted by the individual characteristics of stress responsiveness.

  4. Study of cyclic and steady particle motion in a realistic human airway model using phase-Doppler anemometry

    Directory of Open Access Journals (Sweden)

    Jícha Miroslav

    2012-04-01

    Full Text Available Transport and deposition of particles in human airways has been of research interest for many years. Various experimental methods such as constant temperature anemometry, particle image velocimetry and laser-Doppler based techniques were employed for study of aerosol transport in the past. We use Phase-Doppler Particle Analyser (P/DPA for time resolved size and velocity measurement of liquid aerosol particles in a size range 1 to 8 μm. The di-2ethylhexyl sabacate (DEHS particles were produced by condensation monodisperse aerosol generator. A thin-wall transparent model of human airways with non-symmetric bifurcations and non-planar geometry containing parts from throat to 3rd-4th generation of bronchi was fabricated for the study. Several cyclic (sinusoidal breathing regimes were simulated using pneumatic breathing mechanism. Analogous steady-flow regimes were also investigated and used for comparison. An analysis of the particle velocity data was performed with aim to gain deeper understanding of the transport phenomena in the realistic bifurcating airway system. Flows of particles of different sizes in range 1 – 10 μm was found to slightly differ for extremely high Stokes numbers. Differences in steady and cyclic turbulence intensities were documented in the paper. Systematically higher turbulence intensity was found for cyclic flows and mainly in the expiration breathing phase. Negligible differences were found for behaviour of different particle size classes in the inspected range 1 to 8 μm. Possibility of velocity spectra estimation of air flow using the P/DPA data is discussed.

  5. Regional electric field induced by electroconvulsive therapy in a realistic finite element head model: Influence of white matter anisotropic conductivity

    Science.gov (United States)

    Lee, Won Hee; Deng, Zhi-De; Kim, Tae-Seong; Laine, Andrew F.; Lisanby, Sarah H.; Peterchev, Angel V.

    2012-01-01

    We present the first computational study investigating the electric field (E-field) strength generated by various electroconvulsive therapy (ECT) electrode configurations in specific brain regions of interest (ROIs) that have putative roles in the therapeutic action and/or adverse side effects of ECT. This study also characterizes the impact of the white matter (WM) conductivity anisotropy on the E-field distribution. A finite element head model incorporating tissue heterogeneity and WM anisotropic conductivity was constructed based on structural magnetic resonance imaging (MRI) and diffusion tensor MRI data. We computed the spatial E-field distributions generated by three standard ECT electrode placements including bilateral (BL), bifrontal (BF), and right unilateral (RUL) and an investigational electrode configuration for focal electrically administered seizure therapy (FEAST). The key results are that (1) the median E-field strength over the whole brain is 3.9, 1.5, 2.3, and 2.6 V/cm for the BL, BF, RUL, and FEAST electrode configurations, respectively, which coupled with the broad spread of the BL E-field suggests a biophysical basis for observations of superior efficacy of BL ECT compared to BF and RUL ECT; (2) in the hippocampi, BL ECT produces a median E-field of 4.8 V/cm that is 1.5–2.8 times stronger than that for the other electrode configurations, consistent with the more pronounced amnestic effects of BL ECT; and (3) neglecting the WM conductivity anisotropy results in E-field strength error up to 18% overall and up to 39% in specific ROIs, motivating the inclusion of the WM conductivity anisotropy in accurate head models. This computational study demonstrates how the realistic finite element head model incorporating tissue conductivity anisotropy provides quantitative insight into the biophysics of ECT, which may shed light on the differential clinical outcomes seen with various forms of ECT, and may guide the development of novel stimulation

  6. Long term contaminant migration and impacts from uranium mill tailings. Comparison of computer models using a realistic dataset

    Energy Technology Data Exchange (ETDEWEB)

    Camus, H. [CEA Centre d' Etudes Nucleaires de Fontenay-aux-Roses, 92 (France). Inst. de Protection et de Surete Nucleaire] [and others

    1996-08-01

    This is the final report of the Working Group describing: the enhancement of the previously devised V1 scenario to produce a V2 scenario which includes more detailed source term and other site specific data; the application of models in deterministic and probabilistic mode to calculate contaminant concentrations in biosphere media, and related radiation doses, contaminant intakes and health risks, including estimates of uncertainties; the comparison and analysis of the resulting calculations. A series of scenarios was developed based on data provided by Working Group members from a range of actual tailings disposal sites, culminating in the V2.2 and V2.3 scenarios. The V2.2 and V2.3 scenarios are identical in all respects, except that the V2.2 considers radioactive (U-238 chain) contaminants, whilst the V2.3 considers stable elements (As, Ni, Pb). Since the scenarios are based on data obtained from a range of actual sites, they should be considered to be generically realistic rather than representative of a particular single site. In both scenarios, the contaminants of interest are assumed to be released in leachate from a tailings pile into an underlying aquifer. They are transported in groundwater through the aquifer to a well. Water is abstracted from the well and used for: watering beef cattle; human consumption; and irrigating leafy vegetables. The beef and leafy vegetables are consumed by humans living in the area. The same contaminants are also released into the atmosphere due to the wind erosion of the pile and then deposited upon the soil, pasture and leafy vegetables. In addition, for the V2.2 scenario, Rn-222 is assumed to be released to atmosphere from the pile. Unlike the V1 scenario, no consideration is given to surface water exposure pathways. Results show that there is exceedingly good agreement between participants' deterministic and probabilistic estimates of total dose or intake. They agree within a factor of two to three for both scenarios

  7. Flow in the Inlet Region in Tangential Inlet Cyclones

    NARCIS (Netherlands)

    Peng, W.; Boot, P.J.A.J.; Hoffmann, A.C; Dries, H.W.A.; Kater, J.

    2001-01-01

    In this paper the flow pattern in a tangential inlet cyclone is studied by laser Doppler anemometry, with emphasis on the inlet region. The particular focus is on axial asymmetry in the flow, which was studied by determining radial profiles of the axial and tangential gas velocity components at four

  8. Realistic simulation of reduced-dose CT with noise modeling and sinogram synthesis using DICOM CT images

    Energy Technology Data Exchange (ETDEWEB)

    Won Kim, Chang [Interdisciplinary Program of Bioengineering Major Seoul National University College of Engineering, San 56-1, Silim-dong, Gwanak-gu, Seoul 152-742, South Korea and Institute of Radiation Medicine, Seoul National University College of Medicine, 28, Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Kim, Jong Hyo, E-mail: kimjhyo@snu.ac.kr [Department of Radiology, Institute of Radiation Medicine, Seoul National University College of Medicine, 28, Yongon-dong, Chongno-gu, Seoul, 110-744 (Korea, Republic of); Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Suwon, Gyeonggi-do, 443-270 (Korea, Republic of); Advanced Institutes of Convergence Technology, Seoul National University, Suwon, Gyeonggi-do, 443-270 (Korea, Republic of)

    2014-01-15

    Purpose: Reducing the patient dose while maintaining the diagnostic image quality during CT exams is the subject of a growing number of studies, in which simulations of reduced-dose CT with patient data have been used as an effective technique when exploring the potential of various dose reduction techniques. Difficulties in accessing raw sinogram data, however, have restricted the use of this technique to a limited number of institutions. Here, we present a novel reduced-dose CT simulation technique which provides realistic low-dose images without the requirement of raw sinogram data. Methods: Two key characteristics of CT systems, the noise equivalent quanta (NEQ) and the algorithmic modulation transfer function (MTF), were measured for various combinations of object attenuation and tube currents by analyzing the noise power spectrum (NPS) of CT images obtained with a set of phantoms. Those measurements were used to develop a comprehensive CT noise model covering the reduced x-ray photon flux, object attenuation, system noise, and bow-tie filter, which was then employed to generate a simulated noise sinogram for the reduced-dose condition with the use of a synthetic sinogram generated from a reference CT image. The simulated noise sinogram was filtered with the algorithmic MTF and back-projected to create a noise CT image, which was then added to the reference CT image, finally providing a simulated reduced-dose CT image. The simulation performance was evaluated in terms of the degree of NPS similarity, the noise magnitude, the bow-tie filter effect, and the streak noise pattern at photon starvation sites with the set of phantom images. Results: The simulation results showed good agreement with actual low-dose CT images in terms of their visual appearance and in a quantitative evaluation test. The magnitude and shape of the NPS curves of the simulated low-dose images agreed well with those of real low-dose images, showing discrepancies of less than +/−3.2% in

  9. Aerosol Inlet Characterization Experiment Report

    Energy Technology Data Exchange (ETDEWEB)

    Bullard, Robert L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kuang, Chongai [Brookhaven National Lab. (BNL), Upton, NY (United States); Uin, Janek [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, Scott [Brookhaven National Lab. (BNL), Upton, NY (United States); Springston, Stephen R. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-05-01

    The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility Aerosol Observation System inlet stack was characterized for particle penetration efficiency from 10 nm to 20 μm in diameter using duplicate scanning mobility particle sizers (10 nm-450 nm), ultra-high-sensitivity aerosol spectrometers (60 nm-μm), and aerodynamic particle sizers (0.5 μm-20 μm). Results show good model-measurement agreement and unit transmission efficiency of aerosols from 10 nm to 4 μm in diameter. Large uncertainties in the measured transmission efficiency exist above 4 μm due to low ambient aerosol signal in that size range.

  10. Simple and Realistic Data Generation

    DEFF Research Database (Denmark)

    Pedersen, Kenneth Houkjær; Torp, Kristian; Wind, Rico

    2006-01-01

    This paper presents a generic, DBMS independent, and highly extensible relational data generation tool. The tool can efficiently generate realistic test data for OLTP, OLAP, and data streaming applications. The tool uses a graph model to direct the data generation. This model makes it very simple...

  11. Optimization of multifocal transcranial current stimulation for weighted cortical pattern targeting from realistic modeling of electric fields.

    Science.gov (United States)

    Ruffini, Giulio; Fox, Michael D; Ripolles, Oscar; Miranda, Pedro Cavaleiro; Pascual-Leone, Alvaro

    2014-04-01

    Recently, multifocal transcranial current stimulation (tCS) devices using several relatively small electrodes have been used to achieve more focal stimulation of specific cortical targets. However, it is becoming increasingly recognized that many behavioral manifestations of neurological and psychiatric disease are not solely the result of abnormality in one isolated brain region but represent alterations in brain networks. In this paper we describe a method for optimizing the configuration of multifocal tCS for stimulation of brain networks, represented by spatially extended cortical targets. We show how, based on fMRI, PET, EEG or other data specifying a target map on the cortical surface for excitatory, inhibitory or neutral stimulation and a constraint on the maximal number of electrodes, a solution can be produced with the optimal currents and locations of the electrodes. The method described here relies on a fast calculation of multifocal tCS electric fields (including components normal and tangential to the cortical boundaries) using a five layer finite element model of a realistic head. Based on the hypothesis that the effects of current stimulation are to first order due to the interaction of electric fields with populations of elongated cortical neurons, it is argued that the optimization problem for tCS stimulation can be defined in terms of the component of the electric field normal to the cortical surface. Solutions are found using constrained least squares to optimize current intensities, while electrode number and their locations are selected using a genetic algorithm. For direct current tCS (tDCS) applications, we provide some examples of this technique using an available tCS system providing 8 small Ag/AgCl stimulation electrodes. We demonstrate the approach both for localized and spatially extended targets defined using rs-fcMRI and PET data, with clinical applications in stroke and depression. Finally, we extend these ideas to more general

  12. Realistic Visualization of Virtual Views

    DEFF Research Database (Denmark)

    Livatino, Salvatore

    2005-01-01

    Computer Graphics allows us today to visualize in real-time innumerable and amazing scenarios with no limits on viewpoint and viewing direction. However, to design accurate object models and to simulate all the physical phenomena occurring in analogous real situations often represents a job...... that can be impractical and sometime impossible. In addition, the artificial nature of data often makes visualized virtual scenarios not realistic enough. Not realistic in the sense that a synthetic scene is easy to discriminate visually from a natural scene. A new field of research has consequently...... developed and received much attention in recent years: Realistic Virtual View Synthesis. The main goal is a high fidelity representation of virtual scenarios while easing modeling and physical phenomena simulation. In particular, realism is achieved by the transfer to the novel view of all the physical...

  13. Numerical analysis of wave-induced fluid flow effects related to mesoscopic heterogeneities for realistic models of porous media

    Science.gov (United States)

    Rubino, J. G.; Holliger, K.

    2010-12-01

    suitable upscaling procedure. This computational procedure emulates a corresponding pertinent laboratory experiment, in which a representative, mesoscopic-scale rock sample is subjected to a time-harmonic compressibility test. The thus observed complex volume change of the probed sample then allows for estimating the equivalent complex plane-wave modulus, which in turn yields the corresponding effective phase velocity and quality factor as functions of frequency. We apply this approach to a range of canonical models of porous media characterized by realistic, highly heterogeneous distributions of the hydraulic and/or elastic properties as well as varying levels of saturation. In particular, we also compare the results of spatially continuous variations of the medium and fluid properties with equivalent binary parameter distributions. Interestingly, preliminary results provide evidence to suggest that for most heterogeneous porous media characterized by spatially continuous variations of the hydraulic and/or elastic properties, the contribution of wave-induced mesoscopic fluid flow effects to the velocity dispersion and attenuation of seismic waves is likely to be of subordinate importance.

  14. Managing Algorithmic Skeleton Nesting Requirements in Realistic Image Processing Applications: The Case of the SKiPPER-II Parallel Programming Environment's Operating Model

    Directory of Open Access Journals (Sweden)

    Duculty Florent

    2005-01-01

    Full Text Available SKiPPER is a SKeleton-based Parallel Programming EnviRonment being developed since 1996 and running at LASMEA Laboratory, the Blaise-Pascal University, France. The main goal of the project was to demonstrate the applicability of skeleton-based parallel programming techniques to the fast prototyping of reactive vision applications. This paper deals with the special features embedded in the latest version of the project: algorithmic skeleton nesting capabilities and a fully dynamic operating model. Throughout the case study of a complete and realistic image processing application, in which we have pointed out the requirement for skeleton nesting, we are presenting the operating model of this feature. The work described here is one of the few reported experiments showing the application of skeleton nesting facilities for the parallelisation of a realistic application, especially in the area of image processing. The image processing application we have chosen is a 3D face-tracking algorithm from appearance.

  15. Modeling individual movement decisions of brown hare (Lepus europaeus) as a key concept for realistic spatial behavior and exposure: A population model for landscape-level risk assessment.

    Science.gov (United States)

    Kleinmann, Joachim U; Wang, Magnus

    2017-09-01

    Spatial behavior is of crucial importance for the risk assessment of pesticides and for the assessment of effects of agricultural practice or multiple stressors, because it determines field use, exposition, and recovery. Recently, population models have increasingly been used to understand the mechanisms driving risk and recovery or to conduct landscape-level risk assessments. To include spatial behavior appropriately in population models for use in risk assessments, a new method, "probabilistic walk," was developed, which simulates the detailed daily movement of individuals by taking into account food resources, vegetation cover, and the presence of conspecifics. At each movement step, animals decide where to move next based on probabilities being determined from this information. The model was parameterized to simulate populations of brown hares (Lepus europaeus). A detailed validation of the model demonstrated that it can realistically reproduce various natural patterns of brown hare ecology and behavior. Simulated proportions of time animals spent in fields (PT values) were also comparable to field observations. It is shown that these important parameters for the risk assessment may, however, vary in different landscapes. The results demonstrate the value of using population models to reduce uncertainties in risk assessment and to better understand which factors determine risk in a landscape context. Environ Toxicol Chem 2017;36:2299-2307. © 2017 SETAC. © 2017 SETAC.

  16. Air Motion and Thermal Environment in Pig Housing Facilities with Diffuse Inlet

    DEFF Research Database (Denmark)

    Jacobsen, Lis

    A ventilation system with ambient air supply through diffuse ceiling used in pig production facilities is presented. The climatic conditions were examined both experimentally and numerically in an full scale experimental room and the inlet boundary conditions of the diffuse inlet were examined...... of thermal comfort in terms of the operative temperature of the occupational zone. A model of the boundary condition of the diffuse inlet is necessary because the inlet is a conglomeration of an inlet and a wall boundary condition. Two methods of modelling can be chosen, a model based on the determination...

  17. Shell-side distribution and the influence of inlet conditions in a model of a disc-and-doughnut heat exchanger

    Science.gov (United States)

    Founti, M. A.; Vardis, C.; Whitelaw, J. H.

    1985-09-01

    Measurements of wall pressure and of three orthogonal velocity components with their corresponding fluctuations are reported for two systems of alternating and equi-spaced doughnut and disc baffles axisymmetrically located in a water turbulent pipe flow, simulating the isothermal shell-side flow in shell and tube heat exchangers. The influence of inlet Reynolds number and of asymmetric inlet flow conditions was studied for two geometries. The velocity field was dominated by the pressure gradient and the flow around each individual baffle was influenced by the relative position of its neighbouring baffles.

  18. Modelling and simulation of low-density lipoprotein transport through multi-layered wall of an anatomically realistic carotid artery bifurcation

    Science.gov (United States)

    Kenjereš, Saša; de Loor, Alexander

    2014-01-01

    A high concentration of low-density lipoprotein (LDL) is recognized as one of the principal risk factors for development of atherosclerosis. This paper reports on modelling and simulations of the coupled mass (LDL concentration) and momentum transport through the arterial lumen and the multi-layered arterial wall of an anatomically realistic carotid bifurcation. The mathematical model includes equations for conservation of mass, momentum and concentration, which take into account a porous layer structure, the biological membranes and reactive source/sink terms in different layers of the arterial wall, as proposed in Yang & Vafai (2006). A four-layer wall model of an arterial wall with constant thickness is introduced and initially tested on a simple cylinder geometry where realistic layer properties are specified. Comparative assessment with previously published results demonstrated proper implementation of the mathematical model. Excellent agreement for the velocity and LDL concentration distributions in the arterial lumen and in the artery wall are obtained. Then, an anatomically realistic carotid artery bifurcation is studied. This is the main novelty of the presented research. We find a strong dependence between underlying blood flow pattern (and consequently the wall shear stress distributions) and the uptake of the LDL concentration in the artery wall. The radial dependency of interactions between the diffusion, convection and chemical reactions within the multi-layered artery wall is crucial for accurate predictions of the LDL concentration in the media. It is shown that a four-layer wall model produced qualitatively good agreement with the experimental results of Meyer et al. (1996) in predicting levels of LDL within the media of a rabbit aorta under identical transmural pressure conditions. Finally, it is demonstrated that the adopted model represents a good initial platform for future numerical investigations of the initial stage of atherosclerosis for

  19. Flow Simulation of Supersonic Inlet with Bypass Annular Duct

    Science.gov (United States)

    Kim, HyoungJin; Kumano, Takayasu; Liou, Meng-Sing; Povinelli, Louis A.; Conners, Timothy R.

    2011-01-01

    A relaxed isentropic compression supersonic inlet is a new concept that produces smaller cowl drag than a conventional inlet, but incurs lower total pressure recovery and increased flow distortion in the (radially) outer flowpath. A supersonic inlet comprising a bypass annulus to the relaxed isentropic compression inlet dumps out airflow of low quality through the bypass duct. A reliable computational fluid dynamics solution can provide considerable useful information to ascertain quantitatively relative merits of the concept, and further provide a basis for optimizing the design. For a fast and reliable performance evaluation of the inlet performance, an equivalent axisymmetric model whose area changes accounts for geometric and physical (blockage) effects resulting from the original complex three-dimensional configuration is proposed. In addition, full three-dimensional calculations are conducted for studying flow phenomena and verifying the validity of the equivalent model. The inlet-engine coupling is carried out by embedding numerical propulsion system simulation engine data into the flow solver for interactive boundary conditions at the engine fan face and exhaust plane. It was found that the blockage resulting from complex three-dimensional geometries in the bypass duct causes significant degradation of inlet performance by pushing the terminal normal shock upstream.

  20. Non-linear dynamics of inlet film thickness during unsteady rolling process

    Science.gov (United States)

    Fu, Kuo; Zang, Yong; Gao, Zhiying; Qin, Qin; Wu, Diping

    2016-05-01

    The inlet film thickness directly affects film and stress distribution of rolling interfaces. Unsteady factors, such as unsteady back tension, may disturb the inlet film thickness. However, the current models of unsteady inlet film thickness lack unsteady disturbance factors and do not take surface topography into consideration. In this paper, based on the hydrodynamic analysis of inlet zone an unsteady rolling film model which concerns the direction of surface topography is built up. Considering the small fluctuation of inlet angle, absolute reduction, reduction ratio, inlet strip thickness and roll radius as the input variables and the fluctuation of inlet film thickness as the output variable, the non-linear relationship between the input and output is discussed. The discussion results show that there is 180° phase difference between the inlet film thickness and the input variables, such as the fluctuant absolute reduction, the fluctuant reduction ratio and non-uniform inlet strip thickness, but there is no phase difference between unsteady roll radius and the output. The inlet angle, the steady roll radius and the direction of surface topography have significant influence on the fluctuant amplitude of unsteady inlet film thickness. This study proposes an analysis method for unsteady inlet film thickness which takes surface topography and new disturbance factors into consideration.

  1. Non-invasive estimation and control of inlet pressure in an implantable rotary blood pump for heart failure patients.

    Science.gov (United States)

    Alomari, A H; Savkin, A V; Ayre, P J; Lim, E; Mason, D G; Salamonsen, R F; Fraser, J F; Lovell, N H

    2011-08-01

    We propose a dynamical model for mean inlet pressure estimation in an implantable rotary blood pump during the diastolic period. Non-invasive measurements of pump impeller rotational speed (ω), motor power (P), and pulse width modulation signal acquired from the pump controller were used as inputs to the model. The model was validated over a wide range of speed ramp studies, including (i) healthy (C1), variations in (ii) heart contractility (C2); (iii) afterload (C2, C3, C4), and (iv) preload (C5, C6, C7). Linear regression analysis between estimated and extracted mean inlet pressure obtained from in vivo animal data (greyhound dogs, N = 3) resulted in a highly significant correlation coefficients (R(2) = 0.957, 0.961, 0.958, 0.963, 0.940, 0.946, and 0.959) and mean absolute errors of (e = 1.604, 2.688, 3.667, 3.990, 2.791, 3.215, and 3.225 mmHg) during C1, C2, C3, C4, C5, C6, and C7, respectively. The proposed model was also used to design a controller to regulate mean diastolic pump inlet pressure using non-invasively measured ω and P. In the presence of model uncertainty, the controller was able to track and settle to the desired input within a finite number of sampling periods and minimal error (0.92 mmHg). The model developed herein will play a crucial role in developing a robust control system of the pump that detects and thus avoids undesired pumping states by regulating the inlet pressure within a predefined physiologically realistic limit.

  2. Smart Kd-values, their uncertainties and sensitivities - Applying a new approach for realistic distribution coefficients in geochemical modeling of complex systems.

    Science.gov (United States)

    Stockmann, M; Schikora, J; Becker, D-A; Flügge, J; Noseck, U; Brendler, V

    2017-08-23

    One natural retardation process to be considered in risk assessment for contaminants in the environment is sorption on mineral surfaces. A realistic geochemical modeling is of high relevance in many application areas such as groundwater protection, environmental remediation, or disposal of hazardous waste. Most often concepts with constant distribution coefficients (Kd-values) are applied in geochemical modeling with the advantage to be simple and computationally fast, but not reflecting changes in geochemical conditions. In this paper, we describe an innovative and efficient method, where the smart Kd-concept, a mechanistic approach mainly based on surface complexation modeling, is used (and modified for complex geochemical models) to calculate and apply realistic distribution coefficients. Using the geochemical speciation code PHREEQC, multidimensional smart Kd-matrices are computed as a function of varying (or uncertain) environmental conditions. On the one hand, sensitivity and uncertainty statements for the distribution coefficients can be derived. On the other hand, smart Kd-matrices can be used in reactive transport (or migration) codes (not shown here). This strategy has various benefits: (1) rapid computation of Kd-values for large numbers of environmental parameter combinations; (2) variable geochemistry is taken into account more realistically; (3) efficiency in computing time is ensured, and (4) uncertainty and sensitivity analysis are accessible. Results are presented exemplarily for the sorption of uranium(VI) onto a natural sandy aquifer material and are compared to results based on the conventional Kd-concept. In general, the sorption behavior of U(VI) in dependence of changing geochemical conditions is described quite well. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Performance influence in submersible pump with different diffuser inlet widths

    Directory of Open Access Journals (Sweden)

    Qingshun Wei

    2016-12-01

    Full Text Available The diffuser inlet width is a key geometric parameter that affects submersible pump performance. On the basis of diffuser characteristic curve analyses, diffusers with different inlet widths and the same impeller were equipped to construct a submersible pump model through the use of AutoCAD software. The performance curves of the submersible pump, with six diffuser inlet widths, were obtained using computational fluid dynamics method. Simultaneously, the simulation results were tested with the experimental method presented in this article. The results show that the optimum value of the inlet width (b3 = 50 mm is larger than the experience-based one. With an increase in the inlet width, the optimum operating point of a submersible pump offsets to a larger flow rate. When the guide blade inlet width is approximately 40–55 mm, the submersible pump efficiency is relatively high, approximately 75.9%–83.7% capacity, and the flow rate is approximately 105–135 m3/h. The numerical results of submersible pump performance are higher than those of the test results; however, their change trends have an acceptable agreement with each other. The practical significance is supplied by changing the inlet width of the diffuser to expand the scope of use.

  4. A novel model to assess the efficacy of steam surface pasteurization of cooked surimi gels inoculated with realistic levels of Listeria innocua.

    Science.gov (United States)

    Skåra, Torstein; Valdramidis, Vasilis P; Rosnes, Jan Thomas; Noriega, Estefanía; Van Impe, Jan F M

    2014-12-01

    Steam surface pasteurization is a promising decontamination technology for reducing pathogenic bacteria in different stages of food production. The effect of the artificial inoculation type and initial microbial load, however, has not been thoroughly assessed in the context of inactivation studies. In order to optimize the efficacy of the technology, the aim of this study was to design and validate a model system for steam surface pasteurization, assessing different inoculation methods and realistic microbial levels. More specifically, the response of Listeria innocua, a surrogate organism of Listeria monocytogenes, on a model fish product, and the effect of different inoculation levels following treatments with a steam surface pasteurization system was investigated. The variation in the resulting inoculation level on the samples was too large (77%) for the contact inoculation procedure to be further considered. In contrast, the variation of a drop inoculation procedure was 17%. Inoculation with high levels showed a rapid 1-2 log decrease after 3-5 s, and then no further inactivation beyond 20 s. A low level inoculation study was performed by analysing the treated samples using a novel contact plating approach, which can be performed without sample homogenization and dilution. Using logistic regression, results from this method were used to model the binary responses of Listeria on surfaces with realistic inoculation levels. According to this model, a treatment time of 23 s will result in a 1 log reduction (for P = 0.1).

  5. 基于MRI数据的真实头有限元模型构造方法%Finite Element Modeling of Realistic Human Head from MRI Data

    Institute of Scientific and Technical Information of China (English)

    刘君; 武和雷

    2012-01-01

    The FEM geometry modeling of realistic head is a key issue for the research on FEM-based EEG/MEG. In this paper, by the technology of image segmentation and mesh generation, a methodology is developed to construct this kind of model based on original MRI data. Through this method, a five - layers realistic head FEM model is obtained, and with its application in FEM - based EEG, a satisfying result shows the reliability of the model.%构造人体头部的有限元模型是开展基于有限元素法研究脑电现象的先决条件.利用图像分割和网格剖分技术提出了一种完全基于原始MRI数据的真实头有限元模型构造方法.通过该方法构造了一个包含5种组织的真实头有限元模型,将该模型应用到基于有限元素法的脑电计算中,结果显示利用该方法构造出的模型真实可信.

  6. Inlet throttling effect on the boiling two-phase flow stability in a natural circulation loop with a chimney

    Science.gov (United States)

    Furuya, M.; Inada, F.; Yasuo, A.

    Experiments have been conducted to investigate an effect of inlet restriction on the thermal-hydraulic stability. A Test facility used in this study was designed and constructed to have non-dimensional values that are nearly equal to those of natural circulation BWR. Experimental results showed that driving force of the natural circulation at the stability boundary was described as a function of heat flux and inlet subcooling independent of inlet restriction. In order to extend experimental database regarding thermal-hydraulic stability to different inlet restriction, numerical analysis was carried out based on the homogeneous flow model. Stability maps in reference to the core inlet subcooling and heat flux were presented for various inlet restrictions using the above-mentioned function. Instability region during the inlet subcooling shifted to the higher inlet subcooling with increasing inlet restriction and became larger with increasing heat flux.

  7. Computational Methods for HSCT-Inlet Controls/CFD Interdisciplinary Research

    Science.gov (United States)

    Cole, Gary L.; Melcher, Kevin J.; Chicatelli, Amy K.; Hartley, Tom T.; Chung, Joongkee

    1994-01-01

    A program aimed at facilitating the use of computational fluid dynamics (CFD) simulations by the controls discipline is presented. The objective is to reduce the development time and cost for propulsion system controls by using CFD simulations to obtain high-fidelity system models for control design and as numerical test beds for control system testing and validation. An interdisciplinary team has been formed to develop analytical and computational tools in three discipline areas: controls, CFD, and computational technology. The controls effort has focused on specifying requirements for an interface between the controls specialist and CFD simulations and a new method for extracting linear, reduced-order control models from CFD simulations. Existing CFD codes are being modified to permit time accurate execution and provide realistic boundary conditions for controls studies. Parallel processing and distributed computing techniques, along with existing system integration software, are being used to reduce CFD execution times and to support the development of an integrated analysis/design system. This paper describes: the initial application for the technology being developed, the high speed civil transport (HSCT) inlet control problem; activities being pursued in each discipline area; and a prototype analysis/design system in place for interactive operation and visualization of a time-accurate HSCT-inlet simulation.

  8. Optimal Design of a Subsonic Submerged Inlet

    Science.gov (United States)

    Taskinoglu, Ezgi; Jovanovic, Vasilije; Elliott, Gregory; Knight, Doyle

    2003-11-01

    A multi-objective optimization study based on an epsilon-constraint method is conducted for the design optimization of a subsonic submerged air vehicle inlet. The multi-objective optimization problem is reformulated by minimizing one of the objectives and restricting the other objectives within user specified values. The figures of merits are the engine-face distortion and swirl that determines the inlet/engine compatibility. The distortion index is minimized while the feasible design space is determined by the swirl index. The design variables are the geometrical parameters defining the surface alteration. The design algorithm is driven by a gradient-based optimizer, and is constructed by integrating the optimizer with a solid modeller (Pro/Engineer), a mesh generator (Grid/Pro) and a flow solver (GASPex). The optimizer is CFSQP (C code for Feasible Sequential Quadratic Programming). Integration of the software packages is achieved by a Perl script. In order to verify the numerical results, an experimental setup for the same inlet geometry is prepared to run at the same flow conditions. The presentation will describe the numerical approach and summarize the results.

  9. Inlet Engineering Toolbox

    Science.gov (United States)

    2014-10-31

    tools and models were developed for desktop PC and web-based use, so that District scientists and engineers can complete projects in-house rather...change and sand transport model . GenCade is run in the Surface-water Modeling System (SMS) version 11.1 or higher. Another product is the Sediment...application at Onslow Bay, NC. Figure 2. Sediment budget in SBAS, Galveston, TX. resiliency of coastal dune systems, whether natural or built

  10. A realistic transport model with pressure dependent parameters for gas flow in tight porous media with application to determining shale rock properties

    CERN Document Server

    Ali, Iftikhar

    2016-01-01

    Shale gas recovery has seen a major boom in recent years due to the increasing global energy demands; but the extraction technologies are very expensive. It is therefore important to develop realistic transport modelling and simulation methods, for porous rocks and porous media, that can compliment the field work. Here, a new nonlinear transport model for single phase gas flow in tight porous media is derived, incorporating many important physical processes that occur in such porous systems: continuous flow, transition flow, slip flow, Knudsen diffusion, adsorption and desorption in to and out of the rock material, and a correction for high flow rates (turbulence). This produces a nonlinear advection-diffusion type of partial differential equation (PDE) with pressure dependent model parameters and associated compressibility coefficients, and highly nonlinear apparent convective flux (velocity) and apparent diffusivity. An important application is to the determination of shale rock properties, such as porosity...

  11. Boundary conditions towards realistic simulation of jet engine noise

    Science.gov (United States)

    Dhamankar, Nitin S.

    Strict noise regulations at major airports and increasing environmental concerns have made prediction and attenuation of jet noise an active research topic. Large eddy simulation coupled with computational aeroacoustics has the potential to be a significant research tool for this problem. With the emergence of petascale computer clusters, it is now computationally feasible to include the nozzle geometry in jet noise simulations. In high Reynolds number experiments on jet noise, the turbulent boundary layer on the inner surface of the nozzle separates into a turbulent free shear layer. Inclusion of a nozzle with turbulent inlet conditions is necessary to simulate this phenomenon realistically. This will allow a reasonable comparison of numerically computed noise levels with the experimental results. Two viscous wall boundary conditions are implemented for modeling the nozzle walls. A characteristic-based approach is compared with a computationally cheaper, extrapolation-based formulation. In viscous flow over a circular cylinder under two different regimes, excellent agreement is observed between the results of the two approaches. The results agree reasonably well with reference experimental and numerical results. Both the boundary conditions are thus found to be appropriate, the extrapolation-based formulation having an edge with its low cost. This is followed with the crucial step of generation of a turbulent boundary layer inside the nozzle. A digital filter-based turbulent inflow condition, extended in a new way to non-uniform curvilinear grids is implemented to achieve this. A zero pressure gradient flat plate turbulent boundary layer is simulated at a high Reynolds number to show that the method is capable of producing sustained turbulence. The length of the adjustment region necessary for synthetic inlet turbulence to recover from modeling errors is estimated. A low Reynolds number jet simulation including a round nozzle geometry is performed and the method

  12. Method for Determining Optimum Injector Inlet Geometry

    Science.gov (United States)

    Trinh, Huu P. (Inventor); Myers, W. Neill (Inventor)

    2015-01-01

    A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The method calculates the tangential inlet area for each throttleable stage. The method also uses correlation between the tangential inlet areas and delta pressure values to calculate the spring displacement and variable inlet geometry of a liquid rocket engine swirl injector.

  13. Centrifugal pump inlet pressure site affects measurement.

    Science.gov (United States)

    Augustin, Simon; Horton, Alison; Butt, Warwick; Bennett, Martin; Horton, Stephen

    2010-09-01

    During extracorporeal life support (ECLS), blood is exposed to a myriad of unphysiological factors that can affect outcome. One aspect of this is the sub-atmospheric pressure generated by the ECLS pump and imparted to blood elements along the pump inlet line. This pressure can be measured on the inlet line close to the pump head by adding a connector, or at the venous cannula connection site. We compared the two measurement sites located at both points; between the venous cannula-inlet tubing and inlet tubing-pump, with a range of cannulae and flows. We also investigated the effects on inlet pressure from pump afterload and increasing inlet tubing length.

  14. Dynamics of leaf gas exchange, xylem and phloem transport, water potential and carbohydrate concentration in a realistic 3-D model tree crown.

    Science.gov (United States)

    Nikinmaa, Eero; Sievänen, Risto; Hölttä, Teemu

    2014-09-01

    Tree models simulate productivity using general gas exchange responses and structural relationships, but they rarely check whether leaf gas exchange and resulting water and assimilate transport and driving pressure gradients remain within acceptable physical boundaries. This study presents an implementation of the cohesion-tension theory of xylem transport and the Münch hypothesis of phloem transport in a realistic 3-D tree structure and assesses the gas exchange and transport dynamics. A mechanistic model of xylem and phloem transport was used, together with a tested leaf assimilation and transpiration model in a realistic tree architecture to simulate leaf gas exchange and water and carbohydrate transport within an 8-year-old Scots pine tree. The model solved the dynamics of the amounts of water and sucrose solute in the xylem, cambium and phloem using a fine-grained mesh with a system of coupled ordinary differential equations. The simulations predicted the observed patterns of pressure gradients and sugar concentration. Diurnal variation of environmental conditions influenced tree-level gradients in turgor pressure and sugar concentration, which are important drivers of carbon allocation. The results and between-shoot variation were sensitive to structural and functional parameters such as tree-level scaling of conduit size and phloem unloading. Linking whole-tree-level water and assimilate transport, gas exchange and sink activity opens a new avenue for plant studies, as features that are difficult to measure can be studied dynamically with the model. Tree-level responses to local and external conditions can be tested, thus making the approach described here a good test-bench for studies of whole-tree physiology.

  15. Realistic Approach for Phasor Measurement Unit Placement

    DEFF Research Database (Denmark)

    Rather, Zakir Hussain; Chen, Zhe; Thøgersen, Paul

    2015-01-01

    This paper presents a realistic cost-effectivemodel for optimal placement of phasor measurement units (PMUs) for complete observability of a power system considering practical cost implications. The proposed model considers hidden or otherwise unaccounted practical costs involved in PMU...

  16. Inlet Performance Characteristics from Wind-Tunnel Tests of a 0.10-Scale Air-Induction System Model of the YF-108A Airplane at Mach Numbers of 2.50, 2.76, and 3.00

    Science.gov (United States)

    Blackaby, James R.; Lyman, E. Gene; Altermann, John A., III

    1959-01-01

    Inlet-performance and external-drag-coefficient characteristics are presented without analysis. Effects are shown of variations of fuselage boundary-layer diverter profile, bleed-surface porosity, bleed-exit area, and inlet ramp, and lip angle.

  17. A multiobjective shape optimization study for a subsonic submerged inlet

    Science.gov (United States)

    Taskinoglu, Ezgi S.

    The purpose of the present work is to summarize the findings of a multiobjective shape optimization study conducted for a subsonic submerged air vehicle inlet. The objective functions of the optimization problem are distortion and swirl indices defined by the distribution of flow parameters over the exit cross-section of the inlet. The geometry alteration is performed by placing a protrusion in the shape of a fin on the baseline inlet surface. Thus, the design variables of the optimization problem are chosen to be the geometrical parameters defining the fin protrusion; namely fin height, length and incidence angle. The Trade Off (also known as epsilon-constraint) method is employed for finding the Pareto optimal set formed by the nondominated solutions of the feasible design space. Since the flow domain solution is required for every step along the line search, an automated optimization loop is constructed by integrating the optimizer with a surface modeler, a mesh generator and a flow solver through which the flow parameters over the compressor face are computed. In addition, the trade study for fin protrusion, the analyses and the comparison of the baseline and Pareto optimal solutions are presented and observations concerning grid resolution and convergence behaviour are discussed. The results display an irregular and discontinuous Pareto optimal set. Optimum inlet designs are scattered in two regions from which one representative inlet design is chosen and analyzed. As a result, it is concluded that an inlet designer has two options within the framework of this optimization study: an inlet design with high swirl but low distortion or an inlet design with low swirl but higher distortion.

  18. Modelling hen harrier dynamics to inform human-wildlife conflict resolution: a spatially-realistic, individual-based approach

    National Research Council Canada - National Science Library

    Heinonen, Johannes P M; Palmer, Stephen C F; Redpath, Steve M; Travis, Justin M J

    2014-01-01

    Individual-based models have gained popularity in ecology, and enable simultaneous incorporation of spatial explicitness and population dynamic processes to understand spatio-temporal patterns of populations...

  19. Evaluation of a micro-scale wind model's performance over realistic building clusters using wind tunnel experiments

    Science.gov (United States)

    Zhang, Ning; Du, Yunsong; Miao, Shiguang; Fang, Xiaoyi

    2016-08-01

    The simulation performance over complex building clusters of a wind simulation model (Wind Information Field Fast Analysis model, WIFFA) in a micro-scale air pollutant dispersion model system (Urban Microscale Air Pollution dispersion Simulation model, UMAPS) is evaluated using various wind tunnel experimental data including the CEDVAL (Compilation of Experimental Data for Validation of Micro-Scale Dispersion Models) wind tunnel experiment data and the NJU-FZ experiment data (Nanjing University-Fang Zhuang neighborhood wind tunnel experiment data). The results show that the wind model can reproduce the vortexes triggered by urban buildings well, and the flow patterns in urban street canyons and building clusters can also be represented. Due to the complex shapes of buildings and their distributions, the simulation deviations/discrepancies from the measurements are usually caused by the simplification of the building shapes and the determination of the key zone sizes. The computational efficiencies of different cases are also discussed in this paper. The model has a high computational efficiency compared to traditional numerical models that solve the Navier-Stokes equations, and can produce very high-resolution (1-5 m) wind fields of a complex neighborhood scale urban building canopy (~ 1 km ×1 km) in less than 3 min when run on a personal computer.

  20. Empirical assessment of the validity limits of the surface wave full ray theory using realistic 3-D Earth models

    KAUST Repository

    Parisi, Laura

    2016-02-10

    The surface wave full ray theory (FRT) is an efficient tool to calculate synthetic waveforms of surface waves. It combines the concept of local modes with exact ray tracing as a function of frequency, providing a more complete description of surface wave propagation than the widely used great circle approximation (GCA). The purpose of this study is to evaluate the ability of the FRT approach to model teleseismic long-period surface waveforms (T ∼ 45–150 s) in the context of current 3-D Earth models to empirically assess its validity domain and its scope for future studies in seismic tomography. To achieve this goal, we compute vertical and horizontal component fundamental mode synthetic Rayleigh waveforms using the FRT, which are compared with calculations using the highly accurate spectral element method. We use 13 global earth models including 3-D crustal and mantle structure, which are derived by successively varying the strength and lengthscale of heterogeneity in current tomographic models. For completeness, GCA waveforms are also compared with the spectral element method. We find that the FRT accurately predicts the phase and amplitude of long-period Rayleigh waves (T ∼ 45–150 s) for almost all the models considered, with errors in the modelling of the phase (amplitude) of Rayleigh waves being smaller than 5 per cent (10 per cent) in most cases. The largest errors in phase and amplitude are observed for T ∼ 45 s and for the three roughest earth models considered that exhibit shear wave anomalies of up to ∼20 per cent, which is much larger than in current global tomographic models. In addition, we find that overall the GCA does not predict Rayleigh wave amplitudes well, except for the longest wave periods (T ∼ 150 s) and the smoothest models considered. Although the GCA accurately predicts Rayleigh wave phase for current earth models such as S20RTS and S40RTS, FRT\\'s phase errors are smaller, notably for the shortest wave periods considered (T

  1. Empirical assessment of the validity limits of the surface wave full ray theory using realistic 3-D Earth models

    Science.gov (United States)

    Parisi, Laura; Ferreira, Ana M. G.

    2016-04-01

    The surface wave full ray theory (FRT) is an efficient tool to calculate synthetic waveforms of surface waves. It combines the concept of local modes with exact ray tracing as a function of frequency, providing a more complete description of surface wave propagation than the widely used great circle approximation (GCA). The purpose of this study is to evaluate the ability of the FRT approach to model teleseismic long-period surface waveforms (T ˜ 45-150 s) in the context of current 3-D Earth models to empirically assess its validity domain and its scope for future studies in seismic tomography. To achieve this goal, we compute vertical and horizontal component fundamental mode synthetic Rayleigh waveforms using the FRT, which are compared with calculations using the highly accurate spectral element method. We use 13 global earth models including 3-D crustal and mantle structure, which are derived by successively varying the strength and lengthscale of heterogeneity in current tomographic models. For completeness, GCA waveforms are also compared with the spectral element method. We find that the FRT accurately predicts the phase and amplitude of long-period Rayleigh waves (T ˜ 45-150 s) for almost all the models considered, with errors in the modelling of the phase (amplitude) of Rayleigh waves being smaller than 5 per cent (10 per cent) in most cases. The largest errors in phase and amplitude are observed for T ˜ 45 s and for the three roughest earth models considered that exhibit shear wave anomalies of up to ˜20 per cent, which is much larger than in current global tomographic models. In addition, we find that overall the GCA does not predict Rayleigh wave amplitudes well, except for the longest wave periods (T ˜ 150 s) and the smoothest models considered. Although the GCA accurately predicts Rayleigh wave phase for current earth models such as S20RTS and S40RTS, FRT's phase errors are smaller, notably for the shortest wave periods considered (T ˜ 45 s and

  2. Kuhn: Realist or Antirealist?

    Directory of Open Access Journals (Sweden)

    Michel Ghins

    1998-06-01

    Full Text Available Although Kuhn is much more an antirealist than a realist, the earlier and later articulations of realist and antirealist ingredients in his views merit close scrutiny. What are the constituents of the real invariant World posited by Kuhn and its relation to the mutable paradigm-related worlds? Various proposed solutions to this problem (dubbed the "new-world problem" by Ian Hacking are examined and shown to be unsatisfactory. In The Structure of Scientific Revolutions, the stable World can reasonably be taken to be made up of ordinary perceived objects, whereas in Kuhn's later works the transparadigmatic World is identified with something akin to the Kantian world-in-itself. It is argued that both proposals are beset with insuperable difficulties which render Kuhn's earlier and later versions of antirealism implausible.

  3. Local impact analysis of climate change on precipitation extremes: are high-resolution climate models needed for realistic simulations?

    Science.gov (United States)

    Tabari, Hossein; De Troch, Rozemien; Giot, Olivier; Hamdi, Rafiq; Termonia, Piet; Saeed, Sajjad; Brisson, Erwan; Van Lipzig, Nicole; Willems, Patrick

    2016-09-01

    This study explores whether climate models with higher spatial resolutions provide higher accuracy for precipitation simulations and/or different climate change signals. The outputs from two convection-permitting climate models (ALARO and CCLM) with a spatial resolution of 3-4 km are compared with those from the coarse-scale driving models or reanalysis data for simulating/projecting daily and sub-daily precipitation quantiles. Validation of historical design precipitation statistics derived from intensity-duration-frequency (IDF) curves shows a better match of the convection-permitting model results with the observations-based IDF statistics compared to the driving GCMs and reanalysis data. This is the case for simulation of local sub-daily precipitation extremes during the summer season, while the convection-permitting models do not appear to bring added value to simulation of daily precipitation extremes. Results moreover indicate that one has to be careful in assuming spatial-scale independency of climate change signals for the delta change downscaling method, as high-resolution models may show larger changes in extreme precipitation. These larger changes appear to be dependent on the timescale, since such intensification is not observed for daily timescales for both the ALARO and CCLM models.

  4. Coupling a Mesoscale Numerical Weather Prediction Model with Large-Eddy Simulation for Realistic Wind Plant Aerodynamics Simulations (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    Draxl, C.; Churchfield, M.; Mirocha, J.; Lee, S.; Lundquist, J.; Michalakes, J.; Moriarty, P.; Purkayastha, A.; Sprague, M.; Vanderwende, B.

    2014-06-01

    Wind plant aerodynamics are influenced by a combination of microscale and mesoscale phenomena. Incorporating mesoscale atmospheric forcing (e.g., diurnal cycles and frontal passages) into wind plant simulations can lead to a more accurate representation of microscale flows, aerodynamics, and wind turbine/plant performance. Our goal is to couple a numerical weather prediction model that can represent mesoscale flow [specifically the Weather Research and Forecasting model] with a microscale LES model (OpenFOAM) that can predict microscale turbulence and wake losses.

  5. Quantifying the impact of realistic soil and lake distributions in an Atmosphere-Ocean General Circulation Model simulation of the late Pliocene.

    Science.gov (United States)

    Tindall, Julia; Pound, Matthew; Haywood, Alan; Salzmann, Ulrich

    2013-04-01

    Model simulations of past climates, such as the late Pliocene, are driven by the boundary conditions that were appropriate at the time - if such data is available. The Pliocene Research, Interpretation and Synoptic Mapping dataset, PRISM3, provides boundary conditions for model simulations of the late Pliocene (~3.2ma) and has been used in the Pliocene Palaeoclimate Modelling Intercomparison Project (PlioMIP). In the absence of observational constraints, the PlioMIP simulations assumed that Pliocene lake locations and soil parameters were the same as modern - however in reality there are notable differences between Pliocene and modern lakes and soils. Here we present new global datasets of Pliocene lakes and soils, which can be used to provide more accurate forcing data for climate models. The new datasets are used to drive a 350 year simulation with the Hadley Centre atmosphere-ocean General Circulation Model (GCM), HadCM3. It is shown that using the Pliocene lakes and soils datasets have an impact on the modelled temperature and precipitation, although these effects are spatially localised and are often limited to certain seasons. Changes in Pliocene vegetation patterns that can be attributed to using realistic lakes and soils is also discussed.

  6. Realistic model for a fifth force explaining anomaly in ${^8Be^*} \\to {^8Be} \\;{e^+e^-}$ Decay

    CERN Document Server

    Gu, Pei-Hong

    2016-01-01

    A 6.8$\\sigma$ anomaly has been reported in the opening angle and invariant mass distributions of $e^+e^-$ pairs produced in ${^8Be}$ nuclear transitions. It has been shown that the data can be explained by the existence of a fifth force mediated by a 17 MeV gauge boson X with pure vector current interaction, that is produced in the decay of an excited state to the ground state, ${^8Be^*} \\to {^8Be}\\; X$, and then decays through $X \\to e^+e^-$. We propose a first renormalizable model which is gauge anomaly free to explain the data without introducing new fermions beyond the standard model (SM). Although in this model, $X$ boson also has axial vector current interactions, their contribution cancel out in ${^8Be^*} \\to {^8Be} X$. The model realizes protophobic vector current interaction of $X$ with SM fermions, and is also electron neutrino phobic. Within the allowed parameter space, this model can solve the $(g-2)_\\mu$ anomaly problem. Several other implications are discussed.

  7. Modelling hen harrier dynamics to inform human-wildlife conflict resolution: a spatially-realistic, individual-based approach.

    Directory of Open Access Journals (Sweden)

    Johannes P M Heinonen

    Full Text Available Individual-based models have gained popularity in ecology, and enable simultaneous incorporation of spatial explicitness and population dynamic processes to understand spatio-temporal patterns of populations. We introduce an individual-based model for understanding and predicting spatial hen harrier (Circus cyaneus population dynamics in Great Britain. The model uses a landscape with habitat, prey and game management indices. The hen harrier population was initialised according to empirical census estimates for 1988/89 and simulated until 2030, and predictions for 1998, 2004 and 2010 were compared to empirical census estimates for respective years. The model produced a good qualitative match to overall trends between 1989 and 2010. Parameter explorations revealed relatively high elasticity in particular to demographic parameters such as juvenile male mortality. This highlights the need for robust parameter estimates from empirical research. There are clearly challenges for replication of real-world population trends, but this model provides a useful tool for increasing understanding of drivers of hen harrier dynamics and focusing research efforts in order to inform conflict management decisions.

  8. Stability of realistic strange stars (RSS)

    CERN Document Server

    Bhowmick, S; Dey, M; Ray, S; Ray, R; Bhowmick, Siddhartha; Dey, Jishnu; Dey, Mira; Ray, Subharthi; Ray, Ranjan

    2001-01-01

    Strange stars (SS) calculated from a realistic equation of state (EOS) are very stable, for example under fast rotation but have a soft surface, on which ripples may occur when radiation is emitted close to it. We suggest this as a natural explanation of the fluctuations observed in the intensity profile of X-ray pulsars. In contrast, SS based on EOS derived from the bag models (Bag SS) are less stable against fast rotation and do not have a hard surface and cannot explain these ripples. There are other important differences between Bag SS and the SS, based on a realistic EOS, which we call realistic strange stars (RSS).

  9. Modeling of the global distribution of ionospheric electric fields based on realistic maps of field-aligned currents

    DEFF Research Database (Denmark)

    Lukianova, R.; Christiansen, Freddy

    2006-01-01

    [1] A new approach for modeling the global distribution of ionospheric electric potentials utilizing high-precision maps of FACs derived from measurements by the Orsted and Champ satellites as input to a comprehensive numerical scheme is presented. The boundary conditions provide a correct...

  10. Are Anomalous Stresses in Upper Cook Inlet Basin Linked to the Geometry of the Underlying Subducting Slab? Static and Time-Dependent Stress Models of the 1964 Great Alaska Earthquake

    Science.gov (United States)

    Willis, J. B.

    2010-12-01

    The current stress field of upper Cook Inlet basin is unusual in that the maximum horizontal stress is oriented ~45° counterclockwise from, rather than parallel to, the motion vector of the subducting Pacific Plate. A 3-dimensional, elastic dislocation model of the 1964, Mw 9.2, great Alaska earthquake demonstrates that sharp changes in geometry of the subduction interface may strongly influence the stress field in the upper plate and may account for the anomalous orientation of the principal stresses. The model accurately represents the current view of the 170,000 km2 event as rupturing across a subducted transform boundary that is characterized by complex, rapid changes in slab geometry. Static stress transfer from the 1964 event into the overlying North American plate altered Coulomb stresses on the Lake Clark-Castle Mountain fault system and on several blind, oblique thrust faults that core anticlines of the upper Cook Inlet petroleum province. Each of these faults presents a significant seismic hazard to the greater Anchorage area and to regional petroleum infrastructure and production. Modeled, static Coulomb stress changes caused by the 1964 event suggest a localized decrease in fault stability of the Castle Mountain fault and decreased stability of most east-dipping, upper Cook Inlet thrust faults. Notably, the local region of decreased fault stability along the Castle Mountain fault coincides with rapid changes in the geometry of the underlying subducting slab; models that do not account for changes in slab geometry tend to show increased stability along the length of the fault. The zone of decreased stability correlates with the western segment of the Castle Mountain fault, the only known upper plate fault in the greater Anchorage with unequivocal Holocene surface rupture. A time-dependent rheological, visco-elastic model of the 1964 event suggests that in regions where the subduction interface has not relocked, the regional stress field will evolve for

  11. A 3D self-organizing multicellular epidermis model of barrier formation and hydration with realistic cell morphology based on EPISIM

    Science.gov (United States)

    Sütterlin, Thomas; Tsingos, Erika; Bensaci, Jalil; Stamatas, Georgios N.; Grabe, Niels

    2017-01-01

    The epidermis and the stratum corneum (SC) as its outermost layer have evolved to protect the body from evaporative water loss to the environment. To morphologically represent the extremely flattened cells of the SC - and thereby the epidermal barrier - in a multicellular computational model, we developed a 3D biomechanical model (BM) based on ellipsoid cell shapes. We integrated the BM in the multicellular modelling and simulation platform EPISIM. We created a cell behavioural model (CBM) with EPISIM encompassing regulatory feedback loops between the epidermal barrier, water loss to the environment, and water and calcium flow within the tissue. This CBM allows a small number of stem cells to initiate self-organizing epidermal stratification, yielding the spontaneous emergence of water and calcium gradients comparable to experimental data. We find that the 3D in silico epidermis attains homeostasis most quickly at high ambient humidity, and once in homeostasis the epidermal barrier robustly buffers changes in humidity. Our model yields an in silico epidermis with a previously unattained realistic morphology, whose cell neighbour topology is validated with experimental data obtained from in vivo images. This work paves the way to computationally investigate how an impaired SC barrier precipitates disease. PMID:28262741

  12. Monte-Carlo Simulations of Spin-Crossover Phenomena Based on a Vibronic Ising-like Model with Realistic Parameters

    CERN Document Server

    Ye, Hong-zhou; Jiang, Hong

    2014-01-01

    Materials with spin-crossover (SCO) properties hold great potentials in information storage and therefore have received a lot of concerns in the recent decades. The hysteresis phenomena accompanying SCO is attributed to the intermolecular cooperativity whose underlying mechanism may have a vibronic origin. In this work, a new vibronic Ising-like model in which the elastic coupling between SCO centers is included by considering harmonic stretching and bending (SAB) interactions is proposed and solved by Monte Carlo simulations. The key parameters in the new model, $k_1$ and $k_2$, corresponding to the elastic constant of the stretching and bending mode, respectively, can be directly related to the macroscopic bulk and shear modulus of the material in study, which can be readily estimated either based on experimental measurements or first-principles calculations. The convergence issue in the MC simulations of the thermal hysteresis has been carefully checked, and it was found that the stable hysteresis loop can...

  13. Towards a realistic model of quarks and leptons, leptonic CP violation and neutrinoless $\\beta\\beta$-decay

    CERN Document Server

    Ahn, Y H

    2014-01-01

    In order to explain the fermion masses and mixings naturally, we introduce a specific flavor symmetry and mass suppression pattern that constrain the flavor structure of the fermion Yukawa couplings. Our model describes why the hierarchy of neutrino masses is milder than the hierarchy of charged fermion masses in terms of successive powers of flavon fields. We investigate CP violation and neutrinoless double beta ($0\

  14. How does multiscale modelling and inclusion of realistic palaeobathymetry affect numerical simulation of the Storegga Slide tsunami?

    Science.gov (United States)

    Hill, Jon; Collins, Gareth S.; Avdis, Alexandros; Kramer, Stephan C.; Piggott, Matthew D.

    2014-11-01

    The ∼8.15 ka Storegga submarine slide was a large (∼3000 km3), tsunamigenic slide off the coast of Norway. The resulting tsunami had run-up heights of around 10-20 m on the Norwegian coast, over 12 m in Shetland, 3-6 m on the Scottish mainland coast and reached as far as Greenland. Accurate numerical simulations of Storegga require high spatial resolution near the coasts, particularly near tsunami run-up observations, and also in the slide region. However, as the computational domain must span the whole of the Norwegian-Greenland sea, employing uniformly high spatial resolution is computationally prohibitive. To overcome this problem, we present a multiscale numerical model of the Storegga slide-generated tsunami where spatial resolution varies from 500 m to 50 km across the entire Norwegian-Greenland sea domain to optimally resolve the slide region, important coastlines and bathymetric changes. We compare results from our multiscale model to previous results using constant-resolution models and show that accounting for changes in bathymetry since 8.15 ka, neglected in previous numerical studies of the Storegga slide-tsunami, improves the agreement between the model and inferred run-up heights in specific locations, especially in the Shetlands, where maximum run-up height increased from 8 m (modern bathymetry) to 13 m (palaeobathymetry). By tracking the Storegga tsunami as far south as the southern North sea, we also found that wave heights were high enough to inundate Doggerland, an island in the southern North Sea prior to sea level rise over the last 8 ka.

  15. FreeCAD visualization of realistic 3D physical optics beams within a CAD system-model

    Science.gov (United States)

    Gayer, D.; O'Sullivan, C.; Scully, S.; Burke, D.; Brossard, J.; Chapron, C.

    2016-07-01

    The facility to realise the shape and extent of optical beams within a telescope or beamcombiner can aid greatly in the design and layout of optical elements within the system. It can also greatly facilitate communication between the optical design team and other teams working on the mechanical design of an instrument. Beyond the realm where raytracing is applicable however, it becomes much more difficult to realise accurate 3D beams which incorporate diffraction effects. It then is another issue to incorporate this into a CAD model of the system. A novel method is proposed which has been used to aid with the design of an optical beam combiner for the QUBIC (Q and U Bolometric Interferometer for Cosmology) 1 experiment operating at 150 GHz and 220 GHz. The method combines calculation work in GRASP 2, a commercial physical optics modelling tool from TICRA, geometrical work in Mathematica, and post processing in MATLAB. Finally, the Python console of the open source package FreeCAD3 is exploited to realise the 3D beams in a complete CAD system-model of the QUBIC optical beam combiner. This paper details and explains the work carried out to reach the goal and presents some graphics of the outcome. 3D representations of beams from some back-to-back input horns of the QUBIC instrument are shown within the CAD model. Beams of the -3dB and -13dB contour envelope are shown as well as envelopes enclosing 80% and 95% of the power of the beam. The ability to see these beams in situ with all the other elements of the combiner such as mirrors, cold stop, beam splitter and cryostat widows etc. greatly simplified the design for these elements and facilitated communication of element dimension and location between different subgroups within the QUBIC group.

  16. Development of realistic thermal-hydraulic system analysis codes ; development of thermal hydraulic test requirements for multidimensional flow modeling

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Kune Yull; Yoon, Sang Hyuk; Noh, Sang Woo; Lee, Il Suk [Seoul National University, Seoul (Korea)

    2002-03-01

    This study is concerned with developing a multidimensional flow model required for the system analysis code MARS to more mechanistically simulate a variety of thermal hydraulic phenomena in the nuclear stem supply system. The capability of the MARS code as a thermal hydraulic analysis tool for optimized system design can be expanded by improving the current calculational methods and adding new models. In this study the relevant literature was surveyed on the multidimensional flow models that may potentially be applied to the multidimensional analysis code. Research items were critically reviewed and suggested to better predict the multidimensional thermal hydraulic behavior and to identify test requirements. A small-scale preliminary test was performed in the downcomer formed by two vertical plates to analyze multidimensional flow pattern in a simple geometry. The experimental result may be applied to the code for analysis of the fluid impingement to the reactor downcomer wall. Also, data were collected to find out the controlling parameters for the one-dimensional and multidimensional flow behavior. 22 refs., 40 figs., 7 tabs. (Author)

  17. A Bio-Realistic Finite Element Model to Evaluate the Effect of Masticatory Loadings on Mouse Mandible-Related Tissues

    Directory of Open Access Journals (Sweden)

    Alexander Tsouknidas

    2017-05-01

    Full Text Available Mice are arguably the dominant model organisms for studies investigating the effect of genetic traits on the pathways to mammalian skull and teeth development, thus being integral in exploring craniofacial and dental evolution. The aim of this study is to analyse the functional significance of masticatory loads on the mouse mandible and identify critical stress accumulations that could trigger phenotypic and/or growth alterations in mandible-related structures. To achieve this, a 3D model of mouse skulls was reconstructed based on Micro Computed Tomography measurements. Upon segmenting the main hard tissue components of the mandible such as incisors, molars and alveolar bone, boundary conditions were assigned on the basis of the masticatory muscle architecture. The model was subjected to four loading scenarios simulating different feeding ecologies according to the hard or soft type of food and chewing or gnawing biting movement. Chewing and gnawing resulted in varying loading patterns, with biting type exerting a dominant effect on the stress variations experienced by the mandible and loading intensity correlating linearly to the stress increase. The simulation provided refined insight on the mechanobiology of the mouse mandible, indicating that food consistency could influence micro evolutionary divergence patterns in mandible shape of rodents.

  18. Tidal Motion in a Complex Inlet and Bay System, Ponce de Leon Inlet, Florida

    Science.gov (United States)

    2000-01-01

    REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Tidal Motion in a Complex Inlet and Bay System, Ponce de Leon Inlet, Florida 5a...investigated in Ponce de Leon (Ponce) Inlet, Florida, and its bay channels through a 10-week data-collection campaign and two-dimensional numerical...Beach, Florida Summer 2000 Tidal Motion in a Complex Inlet and Bay System, Ponce de Leon Inlet, Florida Adele Militellot and Gary A. Zarillo:j: t

  19. Fresh tar (from biomass gasification) destruction with downstream catalysts: comparison of their intrinsic activity with a realistic kinetic model

    Energy Technology Data Exchange (ETDEWEB)

    Corella, J.; Narvaez, I.; Orio, A. [Complutense Univ. of Madrid (Spain). Dept. of Chemical Engineering

    1996-12-31

    A model for fresh tar destruction over catalysts placed downstream a biomass gasifier is presented. It includes the stoichio-metry and the calculation of the kinetic constants for the tar destruction. Catalysts studied include commercial Ni steam reforming catalysts and calcinated dolomites. Kinetic constants for tar destruction are calculated for several particle sizes, times- on-stream and temperatures of the catalyst and equivalence ratios in the gasifier. Such intrinsic kinetic constants allow a rigorous or scientific comparison of solids and conditions to be used in an advanced gasification process. (orig.) 4 refs.

  20. Dose conversion coefficients for monoenergetic electrons incident on a realistic human eye model with different lens cell populations

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, P; Vaz, P [Technological and Nuclear Institute, Estrada Nacional No 10, 2686-953 Sacavem (Portugal); Zankl, M; Schlattl, H, E-mail: pedro.nogueira@helmholtz-muenchen.de [Helmholtz Zentrum Muenchen-German Research Center for Environmental Health, Research Unit Medical Radiation Physics and Diagnostics, Ingolstaedter Landstrasse 1, D-85764 Neuherberg (Germany)

    2011-11-07

    The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation-the germinative cells-absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.

  1. A realistic bi-hemispheric model of the cerebellum uncovers the purpose of the abundant granule cells during motor control

    Science.gov (United States)

    Pinzon-Morales, Ruben-Dario; Hirata, Yutaka

    2015-01-01

    The cerebellar granule cells (GCs) have been proposed to perform lossless, adaptive spatio-temporal coding of incoming sensory/motor information required by downstream cerebellar circuits to support motor learning, motor coordination, and cognition. Here we use a physio-anatomically inspired bi-hemispheric cerebellar neuronal network (biCNN) to selectively enable/disable the output of GCs and evaluate the behavioral and neural consequences during three different control scenarios. The control scenarios are a simple direct current motor (1 degree of freedom: DOF), an unstable two-wheel balancing robot (2 DOFs), and a simulation model of a quadcopter (6 DOFs). Results showed that adequate control was maintained with a relatively small number of GCs (< 200) in all the control scenarios. However, the minimum number of GCs required to successfully govern each control plant increased with their complexity (i.e., DOFs). It was also shown that increasing the number of GCs resulted in higher robustness against changes in the initialization parameters of the biCNN model (i.e., synaptic connections and synaptic weights). Therefore, we suggest that the abundant GCs in the cerebellar cortex provide the computational power during the large repertoire of motor activities and motor plants the cerebellum is involved with, and bring robustness against changes in the cerebellar microcircuit (e.g., neuronal connections). PMID:25983678

  2. A realistic bi-hemispheric model of the cerebellum uncovers the purpose of the abundant granule cells during motor control

    Directory of Open Access Journals (Sweden)

    Ruben Dario Pinzon Morales

    2015-05-01

    Full Text Available The cerebellar granule cells (GCs have been proposed to perform lossless, adaptive spatio-temporal coding of incoming sensory/motor information required by downstream cerebellar circuits to textcolor{red}{support} motor learning, motor coordination, and cognition. Here we use a physio-anatomically inspired bi-hemispheric cerebellar neuronal network (biCNN to selectively enable/disable the output of GCs and evaluate the behavioral and neural consequences during three different control scenarios. The control scenarios are a simple direct current motor (1 degree of freedom: DOF, an unstable two-wheel balancing robot (2 DOFs, and a simulation model of a quadcopter (6 DOFs. Results showed that adequate control was maintained with a relatively small number of GCs ($<$ 200 in all the control scenarios. However, the minimum number of GCs required to successfully govern each control plant increased with their complexity (i.e., DOFs. It was also shown that increasing the number of GCs resulted in higher robustness against changes in the initialization parameters of the biCNN model (i.e., synaptic connections and synaptic weights. Therefore, we suggest that the abundant GCs in the cerebellar cortex provide the computational power during the large repertoire of motor activities and motor plants the cerebellum is involved with, and bring robustness against changes in the cerebellar microcircuit (e.g., neuronal connections.

  3. Comparison of realistic and idealized breathing patterns in computational models of airflow and vapor dosimetry in the rodent upper respiratory tract

    Energy Technology Data Exchange (ETDEWEB)

    Colby, Sean M.; Kabilan, Senthil; Jacob, Richard E.; Kuprat, Andrew P.; Einstein, Daniel R.; Corley, Richard A.

    2016-03-17

    Abstract Context: Computational fluid dynamics (CFD) simulations of airflows coupled with physiologically based pharmacokinetic (PBPK) modeling of respiratory tissue doses of airborne materials have traditionally used either steady-state inhalation or a sinusoidal approximation of the breathing cycle for airflow simulations despite their differences from normal breathing patterns. Objective: Evaluate the impact of realistic breathing patterns, including sniffing, on predicted nasal tissue concentrations of a reactive vapor that targets the nose in rats as a case study. Materials and methods: Whole-body plethysmography measurements from a free-breathing rat were used to produce profiles of normal breathing, sniffing and combinations of both as flow inputs to CFD/PBPK simulations of acetaldehyde exposure. Results: For the normal measured ventilation profile, modest reductions in time- and tissue depth-dependent areas under the curve (AUC) acetaldehyde concentrations were predicted in the wet squamous, respiratory and transitional epithelium along the main airflow path, while corresponding increases were predicted in the olfactory epithelium, especially the most distal regions of the ethmoid turbinates, versus the idealized profile. The higher amplitude/frequency sniffing profile produced greater AUC increases over the idealized profile in the olfactory epithelium, especially in the posterior region. Conclusions: The differences in tissue AUCs at known lesion-forming regions for acetaldehyde between normal and idealized profiles were minimal, suggesting that sinusoidal profiles may be used for this chemical and exposure concentration. However, depending upon the chemical, exposure system and concentration and the time spent sniffing, the use of realistic breathing profiles, including sniffing, could become an important modulator for local tissue dose predictions.

  4. Comparison of realistic and idealized breathing patterns in computational models of airflow and vapor dosimetry in the rodent upper respiratory tract.

    Science.gov (United States)

    Colby, Sean M; Kabilan, Senthil; Jacob, Richard E; Kuprat, Andrew P; Einstein, Daniel R; Corley, Richard A

    2016-01-01

    Computational fluid dynamics (CFD) simulations of airflows coupled with physiologically based pharmacokinetic (PBPK) modeling of respiratory tissue doses of airborne materials have traditionally used either steady-state inhalation or a sinusoidal approximation of the breathing cycle for airflow simulations despite their differences from normal breathing patterns. Evaluate the impact of realistic breathing patterns, including sniffing, on predicted nasal tissue concentrations of a reactive vapor that targets the nose in rats as a case study. Whole-body plethysmography measurements from a free-breathing rat were used to produce profiles of normal breathing, sniffing and combinations of both as flow inputs to CFD/PBPK simulations of acetaldehyde exposure. For the normal measured ventilation profile, modest reductions in time- and tissue depth-dependent areas under the curve (AUC) acetaldehyde concentrations were predicted in the wet squamous, respiratory and transitional epithelium along the main airflow path, while corresponding increases were predicted in the olfactory epithelium, especially the most distal regions of the ethmoid turbinates, versus the idealized profile. The higher amplitude/frequency sniffing profile produced greater AUC increases over the idealized profile in the olfactory epithelium, especially in the posterior region. The differences in tissue AUCs at known lesion-forming regions for acetaldehyde between normal and idealized profiles were minimal, suggesting that sinusoidal profiles may be used for this chemical and exposure concentration. However, depending upon the chemical, exposure system and concentration and the time spent sniffing, the use of realistic breathing profiles, including sniffing, could become an important modulator for local tissue dose predictions.

  5. A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions

    Science.gov (United States)

    Mastin, L.G.; Guffanti, M.; Servranckx, R.; Webley, P.; Barsotti, S.; Dean, K.; Durant, A.; Ewert, J.W.; Neri, A.; Rose, William I.; Schneider, D.; Siebert, L.; Stunder, B.; Swanson, G.; Tupper, A.; Volentik, A.; Waythomas, C.F.

    2009-01-01

    During volcanic eruptions, volcanic ash transport and dispersion models (VATDs) are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind. Those models use input parameters, called "eruption source parameters", such as plume height H, mass eruption rate ???, duration D, and the mass fraction m63 of erupted debris finer than about 4??{symbol} or 63????m, which can remain in the cloud for many hours or days. Observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected. Moreover, observed plume height may change during an eruption, requiring rapid assignment of new parameters. This paper reports on a group effort to improve the accuracy of source parameters used by VATDs in the early hours of an eruption. We do so by first compiling a list of eruptions for which these parameters are well constrained, and then using these data to review and update previously studied parameter relationships. We find that the existing scatter in plots of H versus ??? yields an uncertainty within the 50% confidence interval of plus or minus a factor of four in eruption rate for a given plume height. This scatter is not clearly attributable to biases in measurement techniques or to well-recognized processes such as elutriation from pyroclastic flows. Sparse data on total grain-size distribution suggest that the mass fraction of fine debris m63 could vary by nearly two orders of magnitude between small basaltic eruptions (??? 0.01) and large silicic ones (> 0.5). We classify eleven eruption types; four types each for different sizes of silicic and mafic eruptions; submarine eruptions; "brief" or Vulcanian eruptions; and eruptions that generate co-ignimbrite or co-pyroclastic flow plumes. For each eruption type we assign source parameters. We then assign a characteristic eruption type to each of the world's ??? 1500

  6. Combining EEG and MEG for the reconstruction of epileptic activity using a calibrated realistic volume conductor model.

    Directory of Open Access Journals (Sweden)

    Ümit Aydin

    Full Text Available To increase the reliability for the non-invasive determination of the irritative zone in presurgical epilepsy diagnosis, we introduce here a new experimental and methodological source analysis pipeline that combines the complementary information in EEG and MEG, and apply it to data from a patient, suffering from refractory focal epilepsy. Skull conductivity parameters in a six compartment finite element head model with brain anisotropy, constructed from individual MRI data, are estimated in a calibration procedure using somatosensory evoked potential (SEP and field (SEF data. These data are measured in a single run before acquisition of further runs of spontaneous epileptic activity. Our results show that even for single interictal spikes, volume conduction effects dominate over noise and need to be taken into account for accurate source analysis. While cerebrospinal fluid and brain anisotropy influence both modalities, only EEG is sensitive to skull conductivity and conductivity calibration significantly reduces the difference in especially depth localization of both modalities, emphasizing its importance for combining EEG and MEG source analysis. On the other hand, localization differences which are due to the distinct sensitivity profiles of EEG and MEG persist. In case of a moderate error in skull conductivity, combined source analysis results can still profit from the different sensitivity profiles of EEG and MEG to accurately determine location, orientation and strength of the underlying sources. On the other side, significant errors in skull modeling are reflected in EEG reconstruction errors and could reduce the goodness of fit to combined datasets. For combined EEG and MEG source analysis, we therefore recommend calibrating skull conductivity using additionally acquired SEP/SEF data.

  7. Cosmology with massive neutrinos I: towards a realistic modeling of the relation between matter, haloes and galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Villaescusa-Navarro, Francisco; Viel, Matteo [INAF - Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143, Trieste (Italy); Marulli, Federico [Dipartimento di Fisica e Astronomia - Università di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma (Italy); Castorina, Emanuele [SISSA - International School For Advanced Studies, Via Bonomea, 265 34136 Trieste (Italy); Sefusatti, Emiliano [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151, Trieste (Italy); Saito, Shun, E-mail: villaescusa@oats.inaf.it, E-mail: federico.marulli3@unibo.it, E-mail: viel@oats.inaf.it, E-mail: branchin@fis.uniroma3.it, E-mail: ecastori@sissa.it, E-mail: esefusat@ictp.it, E-mail: shun.saito@ipmu.jp [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Chiba 277-8582 (Japan)

    2014-03-01

    By using a suite of large box-size N-body simulations that incorporate massive neutrinos as an extra set of particles, with total masses of 0.15, 0.30, and 0.60 eV, we investigate the impact of neutrino masses on the spatial distribution of dark matter haloes and on the distribution of galaxies within the haloes. We compute the bias between the spatial distribution of dark matter haloes and the overall matter and cold dark matter distributions using statistical tools such as the power spectrum and the two-point correlation function. Overall we find a scale-dependent bias on large scales for the cosmologies with massive neutrinos. In particular, we find that the bias decreases with the scale, being this effect more important for higher neutrino masses and at high redshift. However, our results indicate that the scale-dependence in the bias is reduced if the latter is computed with respect to the cold dark matter distribution only. We find that the value of the bias on large scales is reasonably well reproduced by the Tinker fitting formula once the linear cold dark matter power spectrum is used, instead of the total matter power spectrum. We also investigate whether scale-dependent bias really comes from purely neutrino's effect or from nonlinear gravitational collapse of haloes. For this purpose, we address the Ω{sub ν}-σ{sub 8} degeneracy and find that such degeneracy is not perfect, implying that neutrinos imprint a slight scale dependence on the large-scale bias. Finally, by using a simple halo occupation distribution (HOD) model, we investigate the impact of massive neutrinos on the distribution of galaxies within dark matter haloes. We use the main galaxy sample in the Sloan Digital Sky Survey (SDSS) II Data Release 7 to investigate if the small-scale galaxy clustering alone can be used to discriminate among different cosmological models with different neutrino masses. Our results suggest that different choices of the HOD parameters can reproduce the

  8. Control of Inflow Distortion in a Scarf Inlet

    Science.gov (United States)

    Gerhold, Carl H.; Clark, Lorenzo R.; Biedron, Robert T.

    2002-01-01

    The scarf inlet has the potential to reduce aircraft inlet noise radiation to the ground by reflecting it into the space above the engine. Without forward motion of the engine, the non-symmetry of the inlet causes inflow distortion which generates noise that is greater than the noise reduction of the scarf. However, acoustic evaluations of aircraft engines are often done on static test stands. A method to reduce inflow distortion by boundary layer suction is proposed and evaluated using a model of a high bypass ratio engine located in an anechoic chamber. The design goal of the flow control system is to make the inflow to the inlet circumferentially uniform and to eliminate reversed flow. This minimizes the inflow distortion and allows for acoustic evaluation of the scarf inlet on a static test stand. The inlet boundary layer suction effectiveness is evaluated both by aerodynamic and by acoustic measurements. Although the design goal is not met, the control system is found to have a beneficial effect on the engine operation, reducing blade stall and speed variation. This is quantified by two acoustic benefits, reduction both of the variability of tone noise and of the low frequency wideband noise due to the inflow distortion. It is felt that a compromise in the manufacture of the control hardware contributes to the inability of the control system to perform as expected from the analysis. The control system with sufficient authority is felt to have the potential to permit reliable acoustic testing in a static configuration of engines with non-symmetric inlets. Because the control system can improve operation of the engine, it may also have the potential to reduce noise and vibration and enhance engine longevity during low speed ground operations in the terminal area.

  9. Gravitational Wave Tests of Strong Field General Relativity with Binary Inspirals: Realistic Injections and Optimal Model Selection

    CERN Document Server

    Sampson, Laura; Yunes, Nicolas

    2013-01-01

    We study generic tests of strong-field General Relativity using gravitational waves emitted during the inspiral of compact binaries. Previous studies have considered simple extensions to the standard post-Newtonian waveforms that differ by a single term in the phase. Here we improve on these studies by (i) increasing the realism of injections and (ii) determining the optimal waveform families for detecting and characterizing such signals. We construct waveforms that deviate from those in General Relativity through a series of post-Newtonian terms, and find that these higher-order terms can affect our ability to test General Relativity, in some cases by making it easier to detect a deviation, and in some cases by making it more difficult. We find that simple single-phase post-Einsteinian waveforms are sufficient for detecting deviations from General Relativity, and there is little to be gained from using more complicated models with multiple phase terms. The results found here will help guide future attempts t...

  10. A Realistic Description of Nucleon-Nucleon and Hyperon-Nucleon Interactions in the SU_6 Quark Model

    CERN Document Server

    Fujiwara, Y; Kohno, M; Nakamoto, C; Suzuki, Y

    2001-01-01

    We upgrade a SU_6 quark-model description for the nucleon-nucleon and hyperon-nucleon interactions by improving the effective meson-exchange potentials acting between quarks. For the scalar- and vector-meson exchanges, the momentum-dependent higher-order term is incorporated to reduce the attractive effect of the central interaction at higher energies. The single-particle potentials of the nucleon and Lambda, predicted by the G-matrix calculation, now have proper repulsive behavior in the momentum region q_1=5 - 20 fm^-1. A moderate contribution of the spin-orbit interaction from the scalar-meson exchange is also included. As to the vector mesons, a dominant contribution is the quadratic spin-orbit force generated from the rho-meson exchange. The nucleon-nucleon phase shifts at the non-relativistic energies up to T_lab=350 MeV are greatly improved especially for the 3E states. The low-energy observables of the nucleon-nucleon and the hyperon-nucleon interactions are also reexamined. The isospin symmetry break...

  11. Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system

    NARCIS (Netherlands)

    Lam, N.T.; Stive, M.J.F.; Wang, Z.B.; Verhagen, H.J.; Thuy, V.T.T.

    2008-01-01

    Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system are investigated using numerical models. The ocean forcing including tidal and wave actions and sediment transport is simulated using Delft3D model. Fluvial processes in Delft3D are taken into account as results from SOBEK RU

  12. Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system

    NARCIS (Netherlands)

    Lam, N.T.; Stive, M.J.F.; Wang, Z.B.; Verhagen, H.J.; Thuy, V.T.T.

    2008-01-01

    Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system are investigated using numerical models. The ocean forcing including tidal and wave actions and sediment transport is simulated using Delft3D model. Fluvial processes in Delft3D are taken into account as results from SOBEK

  13. The role of topography in the transformation of spatiotemporal patterns by a large-scale, biologically realistic model of the rat dentate gyrus.

    Science.gov (United States)

    Yu, Gene J; Hendrickson, Phillip J; Robinson, Brian S; Song, Dong; Berger, Theodore W

    2013-01-01

    A large-scale, biologically realistic, computational model of the rat hippocampus is being constructed to study the input-output transformation that the hippocampus performs. In the initial implementation, the layer II entorhinal cortex neurons, which provide the major input to the hippocampus, and the granule cells of the dentate gyrus, which receive the majority of the input, are modeled. In a previous work, the topography, or the wiring diagram, connecting these two populations had been derived and implemented. This paper explores the consequences of two features of the topography, the distribution of the axons and the size of the neurons' axon terminal fields. The topography converts streams of independently generated random Poisson trains into structured spatiotemporal patterns through spatiotemporal convergence achievable by overlapping axon terminal fields. Increasing the axon terminal field lengths allowed input to converge over larger regions of space resulting in granule activation across a greater area but did not increase the total activity as a function of time as the number of targets per input remained constant. Additional simulations demonstrated that the total distribution of spikes in space depends not on the distribution of the presynaptic axons but the distribution of the postsynaptic population. Analyzing spike counts emphasizes the importance of the postsynaptic distribution, but it ignores the fact that each individual input may be carrying unique information. Therefore, a metric should be created that relates and tracks individual inputs as they are propagated and integrated through hippocampus.

  14. Hierarchical Bayesian inference for the EEG inverse problem using realistic FE head models: depth localization and source separation for focal primary currents.

    Science.gov (United States)

    Lucka, Felix; Pursiainen, Sampsa; Burger, Martin; Wolters, Carsten H

    2012-07-16

    The estimation of the activity-related ion currents by measuring the induced electromagnetic fields at the head surface is a challenging and severely ill-posed inverse problem. This is especially true in the recovery of brain networks involving deep-lying sources by means of EEG/MEG recordings which is still a challenging task for any inverse method. Recently, hierarchical Bayesian modeling (HBM) emerged as a unifying framework for current density reconstruction (CDR) approaches comprising most established methods as well as offering promising new methods. Our work examines the performance of fully-Bayesian inference methods for HBM for source configurations consisting of few, focal sources when used with realistic, high-resolution finite element (FE) head models. The main foci of interest are the correct depth localization, a well-known source of systematic error of many CDR methods, and the separation of single sources in multiple-source scenarios. Both aspects are very important in the analysis of neurophysiological data and in clinical applications. For these tasks, HBM provides a promising framework and is able to improve upon established CDR methods such as minimum norm estimation (MNE) or sLORETA in many aspects. For challenging multiple-source scenarios where the established methods show crucial errors, promising results are attained. Additionally, we introduce Wasserstein distances as performance measures for the validation of inverse methods in complex source scenarios.

  15. RFID system for newborn identity reconfirmation in hospital: exposure assessment of a realistic newborn model and effects of the change of the dielectric properties with age.

    Science.gov (United States)

    Fiocchi, Serena; Parazzini, Marta; Ravazzani, Paolo

    2011-12-01

    This paper addresses the exposure assessment of RFID devices for newborn identity reconfirmation. To that purpose, a realistic newborn model ("Baby") is used to evaluate by a computational approach the levels of exposure due to these devices. Considering the average technical specifications currently in use, the exposure matrix in Baby shows that the systems comply with the ICNIRP exposure guidelines. As second aim, the effects of the change of the tissue dielectric properties with age on the so called "exposure matrix" (set of induced magnetic and electric field together with the derived values of SAR) is addressed. Specifically, three different approaches proposed in literature for the age variation of the dielectric properties at 13.56 MHz (the working frequency of the RFID systems for these applications) have been implemented using the Baby geometrical model. The related exposure matrices were then compared with the results obtained using the adult properties. No clear trend can be identified on the exposure matrices obtained varying the dielectric properties at 13.56 MHz, although the results could suggest a trend toward the underestimation of the exposure using adult properties.

  16. Boundary conditions for free surface inlet and outlet problems

    KAUST Repository

    Taroni, M.

    2012-08-10

    We investigate and compare the boundary conditions that are to be applied to free-surface problems involving inlet and outlets of Newtonian fluid, typically found in coating processes. The flux of fluid is a priori known at an inlet, but unknown at an outlet, where it is governed by the local behaviour near the film-forming meniscus. In the limit of vanishing capillary number Ca it is well known that the flux scales with Ca 2/3, but this classical result is non-uniform as the contact angle approaches π. By examining this limit we find a solution that is uniformly valid for all contact angles. Furthermore, by considering the far-field behaviour of the free surface we show that there exists a critical capillary number above which the problem at an inlet becomes over-determined. The implications of this result for the modelling of coating flows are discussed. © 2012 Cambridge University Press.

  17. Scroll-wave dynamics in the presence of ionic and conduction inhomogeneities in an anatomically realistic mathematical model for the pig heart

    Science.gov (United States)

    Majumder, R.; Pandit, R.; Panfilov, A. V.

    2016-12-01

    Nonlinear waves of the reaction-diffusion (RD) type occur in many biophysical systems, including the heart, where they initiate cardiac contraction. Such waves can form vortices called scroll waves, which result in the onset of life-threatening cardiac arrhythmias. The dynamics of scroll waves is affected by the presence of inhomogeneities, which, in a very general way, can be of ionic type, i.e., they affect the reaction part, or conduction type, i.e., they affect the diffusion part of an RD-equation. We demostrate, for the first time, by using a state-of-the-art, anatomically realistic model of the pig heart, how differences in the geometrical and biophysical nature of such inhomogeneities can influence scroll-wave dynamics in different ways. Our study reveals that conduction-type inhomogeneities become increasingly important at small length scales, i.e., in the case of multiple, randomly distributed, obstacles in space at the cellular scale (0.2-0.4mm). Such configurations can lead to scroll-wave break up. In contrast, ionic inhomogeneities, affect scroll-wave dynamics significantly at large length scales, when these inhomogeneities are localized in space at the tissue level (5-10mm). In such configurations, these inhomogeneities can attract scroll waves, by pinning them to the heterogeneity, or lead to scroll-wave breakup.

  18. An investigation of the impact of young children's self-knowledge of trustworthiness on school adjustment: a test of the realistic self-knowledge and positive illusion models.

    Science.gov (United States)

    Betts, Lucy R; Rotenberg, Ken J; Trueman, Mark

    2009-06-01

    The study aimed to examine the relationship between self-knowledge of trustworthiness and young children's school adjustment. One hundred and seventy-three (84 male and 89 female) children from school years 1 and 2 in the United Kingdom (mean age 6 years 2 months) were tested twice over 1-year. Children's trustworthiness was assessed using: (a) self-report at Time 1 and Time 2; (b) peers reports at Time 1 and Time 2; and (c) teacher-reports at Time 2. School adjustment was assessed by child-rated school-liking and the Short-Form Teacher Rating Scale of School Adjustment (Short-Form TRSSA). Longitudinal quadratic relationships were found between school adjustment and children's self-knowledge, using peer-reported trustworthiness as a reference: more accurate self-knowledge of trustworthiness predicted increases in school adjustment. Comparable concurrent quadratic relationships were found between teacher-rated school adjustment and children's self-knowledge, using teacher-reported trustworthiness as a reference, at Time 2. The findings support the conclusion that young children's psychosocial adjustment is best accounted for by the realistic self-knowledge model (Colvin & Block, 1994).

  19. Scroll-wave dynamics in the presence of ionic and conduction inhomogeneities in an anatomically realistic mathematical model for the pig heart

    CERN Document Server

    Majumder, R; Panfilov, A V

    2016-01-01

    Nonlinear waves of the reaction-diffusion (RD) type occur in many biophysical systems, including the heart, where they initiate cardiac contraction. Such waves can form vortices called scroll waves, which result in the onset of life-threatening cardiac arrhythmias. The dynamics of scroll waves is affected by the presence of inhomogeneities, which, in a very general way, can be of \\textit{(i)} ionic type, i.e., they affect the reaction part, or \\textit{(ii)} conduction type, i.e., they affect the diffusion part of an RD equation. We demostrate, for the first time, by using a state-of-the-art, anatomically realistic model of the pig heart, how differences in the geometrical and biophysical nature of such inhomogeneities can influence scroll-wave dynamics in different ways. Our study reveals that conduction-type inhomogeneities become increasingly important at small length scales, i.e., in the case of multiple, randomly distributed, obstacles in space at the cellular scale ($0.2-0.4{\\rm mm}$). Such configuration...

  20. A realistic approach to the evaluation of the quality management movement in health care systems: a comparison between European and African contexts based on Mintzberg's organizational models.

    Science.gov (United States)

    Blaise, P; Kegels, G

    2004-01-01

    The quality movement is gaining momentum worldwide in the field of health care. Initiated in industrialized countries, it steadily grows in Africa. However, there is no evidence that approaches designed to address issues in a given organizational context have the same effect in another one where issues present differently. Along the epistemological paradigm of realistic evaluation proposed by Pawson and Tilley, we use Mintzberg's organizational models to compare the configurations of European and African health care organizations and the trends followed by the quality management movement in both contexts. We illustrate how European health systems traditionally emphasize professional autonomy while African health systems are structured as command and control hierarchical systems. We illustrate how the quality movement in Europe emphasizes standardization of procedures, a characteristic of a mechanistic organization, while excessive standardization is part of the quality problem in Africa. We suggest that instilling professionalism may be a way forward for the quality movement in Africa to improve patient focus and responsiveness of responsible professionals. We also suggest that our interpretation of broad trends and contrasts may be used as a useful departure point to study the wide contextual diversity of the African experience with quality management.

  1. Supporting shared decision-making for older people with multiple health and social care needs: a protocol for a realist synthesis to inform integrated care models.

    Science.gov (United States)

    Bunn, Frances; Goodman, Claire; Manthorpe, Jill; Durand, Marie-Anne; Hodkinson, Isabel; Rait, Greta; Millac, Paul; Davies, Sue L; Russell, Bridget; Wilson, Patricia

    2017-02-07

    Including the patient or user perspective is a central organising principle of integrated care. Moreover, there is increasing recognition of the importance of strengthening relationships among patients, carers and practitioners, particularly for individuals receiving substantial health and care support, such as those with long-term or multiple conditions. The overall aims of this synthesis are to provide a context-relevant understanding of how models to facilitate shared decision-making (SDM) might work for older people with multiple health and care needs, and how they might be applied to integrated care models. The synthesis draws on the principles of realist inquiry, to explain how, in what contexts and for whom, interventions that aim to strengthen SDM among older patients, carers and practitioners are effective. We will use an iterative, stakeholder-driven, three-phase approach. Phase 1: development of programme theory/theories that will be tested through a first scoping of the literature and consultation with key stakeholder groups; phase 2: systematic searches of the evidence to test and develop the theories identified in phase 1; phase 3: validation of programme theory/theories with a purposive sample of participants from phase 1. The synthesis will draw on prevailing theories such as candidacy, self-efficacy, personalisation and coproduction. Ethics approval for the stakeholder interviews was obtained from the University of Hertfordshire ECDA (Ethics Committee with Delegated Authority), reference number HSK/SF/UH/02387. The propositions arising from this review will be used to develop recommendations about how to tailor SDM interventions to older people with complex health and social care needs in an integrated care setting. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  2. Supporting shared decision-making for older people with multiple health and social care needs: a protocol for a realist synthesis to inform integrated care models

    Science.gov (United States)

    Bunn, Frances; Goodman, Claire; Manthorpe, Jill; Durand, Marie-Anne; Hodkinson, Isabel; Rait, Greta; Millac, Paul; Davies, Sue L; Russell, Bridget; Wilson, Patricia

    2017-01-01

    Introduction Including the patient or user perspective is a central organising principle of integrated care. Moreover, there is increasing recognition of the importance of strengthening relationships among patients, carers and practitioners, particularly for individuals receiving substantial health and care support, such as those with long-term or multiple conditions. The overall aims of this synthesis are to provide a context-relevant understanding of how models to facilitate shared decision-making (SDM) might work for older people with multiple health and care needs, and how they might be applied to integrated care models. Methods and analysis The synthesis draws on the principles of realist inquiry, to explain how, in what contexts and for whom, interventions that aim to strengthen SDM among older patients, carers and practitioners are effective. We will use an iterative, stakeholder-driven, three-phase approach. Phase 1: development of programme theory/theories that will be tested through a first scoping of the literature and consultation with key stakeholder groups; phase 2: systematic searches of the evidence to test and develop the theories identified in phase 1; phase 3: validation of programme theory/theories with a purposive sample of participants from phase 1. The synthesis will draw on prevailing theories such as candidacy, self-efficacy, personalisation and coproduction. Ethics and dissemination Ethics approval for the stakeholder interviews was obtained from the University of Hertfordshire ECDA (Ethics Committee with Delegated Authority), reference number HSK/SF/UH/02387. The propositions arising from this review will be used to develop recommendations about how to tailor SDM interventions to older people with complex health and social care needs in an integrated care setting. PMID:28174225

  3. External-Compression Supersonic Inlet Design Code

    Science.gov (United States)

    Slater, John W.

    2011-01-01

    A computer code named SUPIN has been developed to perform aerodynamic design and analysis of external-compression, supersonic inlets. The baseline set of inlets include axisymmetric pitot, two-dimensional single-duct, axisymmetric outward-turning, and two-dimensional bifurcated-duct inlets. The aerodynamic methods are based on low-fidelity analytical and numerical procedures. The geometric methods are based on planar geometry elements. SUPIN has three modes of operation: 1) generate the inlet geometry from a explicit set of geometry information, 2) size and design the inlet geometry and analyze the aerodynamic performance, and 3) compute the aerodynamic performance of a specified inlet geometry. The aerodynamic performance quantities includes inlet flow rates, total pressure recovery, and drag. The geometry output from SUPIN includes inlet dimensions, cross-sectional areas, coordinates of planar profiles, and surface grids suitable for input to grid generators for analysis by computational fluid dynamics (CFD) methods. The input data file for SUPIN and the output file from SUPIN are text (ASCII) files. The surface grid files are output as formatted Plot3D or stereolithography (STL) files. SUPIN executes in batch mode and is available as a Microsoft Windows executable and Fortran95 source code with a makefile for Linux.

  4. Comparison of electric field strength and spatial distribution of electroconvulsive therapy and magnetic seizure therapy in a realistic human head model

    Science.gov (United States)

    Lee, Won Hee; Lisanby, Sarah H.; Laine, Andrew F.; Peterchev, Angel V.

    2017-01-01

    Background This study examines the strength and spatial distribution of the electric field induced in the brain by electroconvulsive therapy (ECT) and magnetic seizure therapy (MST). Methods The electric field induced by standard (bilateral, right unilateral, and bifrontal) and experimental (focal electrically administered seizure therapy and frontomedial) ECT electrode configurations as well as a circular MST coil configuration was simulated in an anatomically realistic finite element model of the human head. Maps of the electric field strength relative to an estimated neural activation threshold were used to evaluate the stimulation strength and focality in specific brain regions of interest for these ECT and MST paradigms and various stimulus current amplitudes. Results The standard ECT configurations and current amplitude of 800–900 mA produced the strongest overall stimulation with median of 1.8–2.9 times neural activation threshold and more than 94% of the brain volume stimulated at suprathreshold level. All standard ECT electrode placements exposed the hippocampi to suprathreshold electric field, although there were differences across modalities with bilateral and right unilateral producing respectively the strongest and weakest hippocampal stimulation. MST stimulation is up to 9 times weaker compared to conventional ECT, resulting in direct activation of only 21% of the brain. Reducing the stimulus current amplitude can make ECT as focal as MST. Conclusions The relative differences in electric field strength may be a contributing factor for the cognitive sparing observed with right unilateral compared to bilateral ECT, and MST compared to right unilateral ECT. These simulations could help understand the mechanisms of seizure therapies and develop interventions with superior risk/benefit ratio. PMID:27318858

  5. Light scattering by complex particles in the Moon's exosphere: Toward a taxonomy of models for the realistic simulation of the scattering behavior of lunar dust

    Science.gov (United States)

    Richard, D. T.; Glenar, D. A.; Stubbs, T. J.; Davis, S. S.; Colaprete, A.

    2011-11-01

    It is suspected that the lunar exosphere has a dusty component dispersed above the surface by various physical mechanisms. Most of the evidence for this phenomenon comes from observations of "lunar horizon glow" (LHG), which is thought to be produced by the scattering of sunlight by this exospheric dust. The characterization of exospheric dust populations at the Moon is key to furthering our understanding of fundamental surface processes, as well as a necessary requirement for the planning of future robotic and human exploration. We present a model to simulate the scattering of sunlight by complex lunar dust grains (i.e. grains that are non-spherical and can be inhomogeneous in composition) to be used in the interpretation of remote sensing data from current and future lunar missions. We numerically model lunar dust grains with several different morphologies and compositions and compute their individual scattering signatures using the Discrete Dipole Approximation (DDA). These scattering properties are then used in a radiative transfer code to simulate the light scattering due to a dust size distribution, as would likely be observed in the lunar exosphere at high altitudes 10's of km. We demonstrate the usefulness and relevance of our model by examining mode: irregular grains, aggregate of spherical monomers and spherical grains with nano-phase iron inclusions. We subsequently simulate the scattering by two grain size distributions ( 0.1 and 0.3μm radius), and show the results normalized per-grain. A similar methodology can also be applied to the analysis of the LHG observations, which are believed to be produced by scattering from larger dust grains within about a meter of the surface. As expected, significant differences in scattering properties are shown between the analyses employing the widely used Mie theory and our more realistic grain geometries. These differences include large variations in intensity as well as a positive polarization of scattered

  6. The role of crown architecture for light harvesting and carbon gain in extreme light environments assessed with a structurally realistic 3-D model

    Directory of Open Access Journals (Sweden)

    Valladares, Fernando

    2000-06-01

    Full Text Available Main results from different studies of crown architecture adaptation to extreme light environments are presented. Light capture and carbon gain by plants from low (forest understory and high (open Mediterranean-type ecosystems light environments were simulated with a 3-D model (YPLANT, which was developed specifically to analyse the structural features that determine light interception and photosynthesis at the whole plant level. Distantly related taxa with contrasting architectures exhibited similar efficiencies of light interception (functional convergence. Between habitats large differences in architecture existed depending on whether light capture must be maximised or whether excess photon flux density must be avoided. These differences are realised both at the species level and within a species because of plastic adjustments of crown architecture to the external light environment. Realistic, 3-D architectural models are indispensable tools in this kind of comparative studies due to the intrinsic complexity of plant architecture. Their efficient development requires a fluid exchange of ideas between botanists, ecologists and plant modellers.Se presentan los resultados principales de varios estudios sobre las adaptaciones del follaje a ambientes lumínicos extremos. Plantas de ambientes oscuros (sotobosques de bosques templados y tropicales y de ambientes muy luminosos (ecosistemas abiertos de tipo Mediterráneo han sido estudiadas mediante un modelo (YPLANT que permite la reconstrucción tridimensional de la parte aérea de las plantas e identificar los rasgos estructurales que determinan la interceptación de luz y la fotosíntesis y transpiraci6n potencial a nivel de toda la copa. Taxones no relacionados y con arquitecturas muy diferentes mostraron una eficiencia en la interceptaci6n de luz similar (convergencia funcional. La comparación entre hábitat revelo grandes diferencias arquitecturales dependiendo de si la absorción de luz deb

  7. Realistic Dirac Leptogenesis

    CERN Document Server

    Murayama, H; Murayama, Hitoshi; Pierce, Aaron

    2002-01-01

    We present a model of leptogenesis that preserves lepton number. The model maintains the important feature of more traditional leptogenesis scenarios: the decaying particles that provide the CP violation necessary for baryogenesis also provide the explanation for the smallness of the neutrino Yukawa couplings. This model clearly demonstrates that, contrary to conventional wisdom, neutrinos need not be Majorana in nature in order to help explain the baryon asymmetry of the universe.

  8. Micro-Ramps for External Compression Low-Boom Inlets

    Science.gov (United States)

    Rybalko, Michael; Loth, Eric; Chima, Rodrick V.; Hirt, Stefanie M.; DeBonis, James R.

    2010-01-01

    The application of vortex generators for flow control in an external compression, axisymmetric, low-boom concept inlet was investigated using RANS simulations with three-dimensional (3-D), structured, chimera (overset) grids and the WIND-US code. The low-boom inlet design is based on previous scale model 1- by 1-ft wind tunnel tests and features a zero-angle cowl and relaxed isentropic compression centerbody spike, resulting in defocused oblique shocks and a weak terminating normal shock. Validation of the methodology was first performed for micro-ramps in supersonic flow on a flat plate with and without oblique shocks. For the inlet configuration, simulations with several types of vortex generators were conducted for positions both upstream and downstream of the terminating normal shock. The performance parameters included incompressible axisymmetric shape factor, separation area, inlet pressure recovery, and massflow ratio. The design of experiments (DOE) methodology was used to select device size and location, analyze the resulting data, and determine the optimal choice of device geometry. The optimum upstream configuration was found to substantially reduce the post-shock separation area but did not significantly impact recovery at the aerodynamic interface plane (AIP). Downstream device placement allowed for fuller boundary layer velocity profiles and reduced distortion. This resulted in an improved pressure recovery and massflow ratio at the AIP compared to the baseline solid-wall configuration.

  9. Physics of Acoustic Radiation from Jet Engine Inlets

    Science.gov (United States)

    Tam, Christopher K. W.; Parrish, Sarah A.; Envia, Edmane; Chien, Eugene W.

    2012-01-01

    Numerical simulations of acoustic radiation from a jet engine inlet are performed using advanced computational aeroacoustics (CAA) algorithms and high-quality numerical boundary treatments. As a model of modern commercial jet engine inlets, the inlet geometry of the NASA Source Diagnostic Test (SDT) is used. Fan noise consists of tones and broadband sound. This investigation considers the radiation of tones associated with upstream propagating duct modes. The primary objective is to identify the dominant physical processes that determine the directivity of the radiated sound. Two such processes have been identified. They are acoustic diffraction and refraction. Diffraction is the natural tendency for an acoustic wave to follow a curved solid surface as it propagates. Refraction is the turning of the direction of propagation of sound waves by mean flow gradients. Parametric studies on the changes in the directivity of radiated sound due to variations in forward flight Mach number and duct mode frequency, azimuthal mode number, and radial mode number are carried out. It is found there is a significant difference in directivity for the radiation of the same duct mode from an engine inlet when operating in static condition and in forward flight. It will be shown that the large change in directivity is the result of the combined effects of diffraction and refraction.

  10. Gas Turbine Engine Inlet Wall Design

    Science.gov (United States)

    Florea, Razvan Virgil (Inventor); Matalanis, Claude G. (Inventor); Stucky, Mark B. (Inventor)

    2016-01-01

    A gas turbine engine has an inlet duct formed to have a shape with a first ellipse in one half and a second ellipse in a second half. The second half has an upstream most end which is smaller than the first ellipse. The inlet duct has a surface defining the second ellipse which curves away from the first ellipse, such that the second ellipse is larger at an intermediate location. The second ellipse is even larger at a downstream end of the inlet duct leading into a fan.

  11. CFD modeling and experimental verification of a single-stage coaxial Stirling-type pulse tube cryocooler without either double-inlet or multi-bypass operating at 30-35 K using mixed stainless steel mesh regenerator matrices

    Science.gov (United States)

    Dang, Haizheng; Zhao, Yibo

    2016-09-01

    This paper presents the CFD modeling and experimental verifications of a single-stage inertance tube coaxial Stirling-type pulse tube cryocooler operating at 30-35 K using mixed stainless steel mesh regenerator matrices without either double-inlet or multi-bypass. A two-dimensional axis-symmetric CFD model with the thermal non-equilibrium mode is developed to simulate the internal process, and the underlying mechanism of significantly reducing the regenerator losses with mixed matrices is discussed in detail based on the given six cases. The modeling also indicates that the combination of the given different mesh segments can be optimized to achieve the highest cooling efficiency or the largest exergy ratio, and then the verification experiments are conducted in which the satisfactory agreements between simulated and tested results are observed. The experiments achieve a no-load temperature of 27.2 K and the cooling power of 0.78 W at 35 K, or 0.29 W at 30 K, with an input electric power of 220 W and a reject temperature of 300 K.

  12. A One Dimensional, Time Dependent Inlet/Engine Numerical Simulation for Aircraft Propulsion Systems

    Science.gov (United States)

    Garrard, Doug; Davis, Milt, Jr.; Cole, Gary

    1999-01-01

    The NASA Lewis Research Center (LeRC) and the Arnold Engineering Development Center (AEDC) have developed a closely coupled computer simulation system that provides a one dimensional, high frequency inlet/engine numerical simulation for aircraft propulsion systems. The simulation system, operating under the LeRC-developed Application Portable Parallel Library (APPL), closely coupled a supersonic inlet with a gas turbine engine. The supersonic inlet was modeled using the Large Perturbation Inlet (LAPIN) computer code, and the gas turbine engine was modeled using the Aerodynamic Turbine Engine Code (ATEC). Both LAPIN and ATEC provide a one dimensional, compressible, time dependent flow solution by solving the one dimensional Euler equations for the conservation of mass, momentum, and energy. Source terms are used to model features such as bleed flows, turbomachinery component characteristics, and inlet subsonic spillage while unstarted. High frequency events, such as compressor surge and inlet unstart, can be simulated with a high degree of fidelity. The simulation system was exercised using a supersonic inlet with sixty percent of the supersonic area contraction occurring internally, and a GE J85-13 turbojet engine.

  13. Microjet flow control in an ultra-compact serpentine inlet

    Institute of Scientific and Technical Information of China (English)

    Da Xingy; Fan Zhaolin; Fan Jianchao; Zeng Liquan; Rui Wei; Zhou Run

    2015-01-01

    Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interface plane (AIP) face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control (MFC) effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90? circumferential distortion pattern to 180? circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the momentum coefficient affects the control effectiveness in a dual stepping manner.

  14. Microjet flow control in an ultra-compact serpentine inlet

    Directory of Open Access Journals (Sweden)

    Da Xingya

    2015-10-01

    Full Text Available Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interface plane (AIP face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control (MFC effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the momentum coefficient affects the control effectiveness in a dual stepping manner.

  15. RAMESES publication standards: realist syntheses

    Directory of Open Access Journals (Sweden)

    Wong Geoff

    2013-01-01

    Full Text Available Abstract Background There is growing interest in realist synthesis as an alternative systematic review method. This approach offers the potential to expand the knowledge base in policy-relevant areas - for example, by explaining the success, failure or mixed fortunes of complex interventions. No previous publication standards exist for reporting realist syntheses. This standard was developed as part of the RAMESES (Realist And MEta-narrative Evidence Syntheses: Evolving Standards project. The project's aim is to produce preliminary publication standards for realist systematic reviews. Methods We (a collated and summarized existing literature on the principles of good practice in realist syntheses; (b considered the extent to which these principles had been followed by published syntheses, thereby identifying how rigor may be lost and how existing methods could be improved; (c used a three-round online Delphi method with an interdisciplinary panel of national and international experts in evidence synthesis, realist research, policy and/or publishing to produce and iteratively refine a draft set of methodological steps and publication standards; (d provided real-time support to ongoing realist syntheses and the open-access RAMESES online discussion list so as to capture problems and questions as they arose; and (e synthesized expert input, evidence syntheses and real-time problem analysis into a definitive set of standards. Results We identified 35 published realist syntheses, provided real-time support to 9 on-going syntheses and captured questions raised in the RAMESES discussion list. Through analysis and discussion within the project team, we summarized the published literature and common questions and challenges into briefing materials for the Delphi panel, comprising 37 members. Within three rounds this panel had reached consensus on 19 key publication standards, with an overall response rate of 91%. Conclusion This project used multiple

  16. Large Eddy Simulation and Reynolds-Averaged Navier-Stokes modeling of flow in a realistic pharyngeal airway model: an investigation of obstructive sleep apnea.

    Science.gov (United States)

    Mihaescu, Mihai; Murugappan, Shanmugam; Kalra, Maninder; Khosla, Sid; Gutmark, Ephraim

    2008-07-19

    Computational fluid dynamics techniques employing primarily steady Reynolds-Averaged Navier-Stokes (RANS) methodology have been recently used to characterize the transitional/turbulent flow field in human airways. The use of RANS implies that flow phenomena are averaged over time, the flow dynamics not being captured. Further, RANS uses two-equation turbulence models that are not adequate for predicting anisotropic flows, flows with high streamline curvature, or flows where separation occurs. A more accurate approach for such flow situations that occur in the human airway is Large Eddy Simulation (LES). The paper considers flow modeling in a pharyngeal airway model reconstructed from cross-sectional magnetic resonance scans of a patient with obstructive sleep apnea. The airway model is characterized by a maximum narrowing at the site of retropalatal pharynx. Two flow-modeling strategies are employed: steady RANS and the LES approach. In the RANS modeling framework both k-epsilon and k-omega turbulence models are used. The paper discusses the differences between the airflow characteristics obtained from the RANS and LES calculations. The largest discrepancies were found in the axial velocity distributions downstream of the minimum cross-sectional area. This region is characterized by flow separation and large radial velocity gradients across the developed shear layers. The largest difference in static pressure distributions on the airway walls was found between the LES and the k-epsilon data at the site of maximum narrowing in the retropalatal pharynx.

  17. Phosphorus mass balance in a highly eutrophic semi-enclosed inlet near a big metropolis: a small inlet can contribute towards particulate organic matter production.

    Science.gov (United States)

    Asaoka, Satoshi; Yamamoto, Tamiji

    2011-01-01

    Terrigenous loading into enclosed water bodies has been blamed for eutrophic conditions marked by massive algal growth and subsequent hypoxia due to decomposition of dead algal cells. This study aims to describe the eutrophication and hypoxia processes in a semi-enclosed water body lying near a big metropolis. Phosphorus mass balance in a small inlet, Ohko Inlet, located at the head of Hiroshima Bay, Japan, was quantified using a numerical model. Dissolved inorganic phosphorous inflow from Kaita Bay next to the inlet was five times higher than that from terrigenous load, which may cause an enhancement of primary production. Therefore, it was concluded that not only the reduction of material load from the land and the suppression of benthic flux are needed, but also reducing the inflow of high phosphorus and oxygen depleted water from Kaita Bay will form a collective alternative measure to remediate the environmental condition of the inlet.

  18. Annual report, Cook Inlet District, 1958 season

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Commercial fishery management activities for Cook Inlet and Resurrection Bay for 1958, including lists of operators and extensive statistics.

  19. Annual report, Cook Inlet District, 1956 season

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Commercial fishery management activities for Cook Inlet and Resurrection Bay for 1956, including lists of operators and extensive statistics.

  20. Annual report, Cook Inlet District, 1954 season

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Commercial fishery management activities for Cook Inlet and Resurrection Bay for 1954, including lists of operators and extensive statistics.

  1. Annual report, Cook Inlet District, 1957 season

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Commercial fishery management activities for Cook Inlet and Resurrection Bay for 1957, including lists of operators and extensive statistics.

  2. Annual report, Cook Inlet District, 1959 season

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Commercial fishery management activities for Cook Inlet and Resurrection Bay for 1959, including lists of operators and extensive statistics.

  3. Constructing probabilistic models for realistic velocity distributions based on forward modeling and tomographic inversion: applications for active and passive source observation schemes

    Science.gov (United States)

    Koulakov, I. Yu.

    2009-04-01

    Seismic tomography is like a photography taken by a camera with deformed and blurred lenses. In the resulting tomograms, colors (amplitudes of anomalies) and shapes of objects are often strongly biased and are usually not representing the reality. We propose an approach which allows investigating properties of the "camera" and retrieving most probable shapes and amplitudes of anomalies in the real Earth. The main idea of this approach is to construct a synthetic model which, after performing forward modeling and tomographic inversion, reproduces the same amplitudes and shapes of patterns as after inversion of observed data. In this modeling, the conditions of the tomographic inversion (damping, grid spacing, source location parameters etc) should be absolutely identical to the case of the observed data processing. The a priori information, if available any, should be taken into account in this modeling to decrease the uncertainty related to fundamental non-uniqueness of the inversion problem. In the talk, several examples of applying this approach at various scales for different data schemes are presented: (1) regional scheme which uses the global data of the ISC catalogue (with examples of regional upper mantle models in Europe and central Asia); (2) local earthquake tomography scheme (illustrated with models in Toba caldera area and in Central Java); (3) seismic profiling which is based on active source refraction travel time data (with examples of several deep seismic sounding profiles in Central Pacific and subduction zones in Chile).

  4. Modeling and Identification of a Realistic Spiking Neural Network and Musculoskeletal Model of the Human Arm, and an Application to the Stretch Reflex.

    Science.gov (United States)

    Sreenivasa, Manish; Ayusawa, Ko; Nakamura, Yoshihiko

    2016-05-01

    This study develops a multi-level neuromuscular model consisting of topological pools of spiking motor, sensory and interneurons controlling a bi-muscular model of the human arm. The spiking output of motor neuron pools were used to drive muscle actions and skeletal movement via neuromuscular junctions. Feedback information from muscle spindles were relayed via monosynaptic excitatory and disynaptic inhibitory connections, to simulate spinal afferent pathways. Subject-specific model parameters were identified from human experiments by using inverse dynamics computations and optimization methods. The identified neuromuscular model was used to simulate the biceps stretch reflex and the results were compared to an independent dataset. The proposed model was able to track the recorded data and produce dynamically consistent neural spiking patterns, muscle forces and movement kinematics under varying conditions of external forces and co-contraction levels. This additional layer of detail in neuromuscular models has important relevance to the research communities of rehabilitation and clinical movement analysis by providing a mathematical approach to studying neuromuscular pathology.

  5. Exophobic quasi-realistic heterotic string vacua

    Energy Technology Data Exchange (ETDEWEB)

    Assel, Benjamin [Centre de Physique Theorique, Ecole Polytechnique, F-91128 Palaiseau (France); Christodoulides, Kyriakos [Dept. of Mathematical Sciences, University of Liverpool, Liverpool L69 7ZL (United Kingdom); Faraggi, Alon E., E-mail: faraggi@amtp.liv.ac.u [Dept. of Mathematical Sciences, University of Liverpool, Liverpool L69 7ZL (United Kingdom); Kounnas, Costas [Lab. Physique Theorique, Ecole Normale Superieure, F-75231 Paris 05 (France); Rizos, John [Department of Physics, University of Ioannina, GR45110 Ioannina (Greece)

    2010-01-25

    We demonstrate the existence of heterotic string vacua that are free of massless exotic fields. The need to break the non-Abelian GUT symmetries in k=1 heterotic string models by Wilson lines, while preserving the GUT embedding of the weak hypercharge and the GUT prediction sin{sup 2}theta{sub w}(M{sub GUT})=3/8, necessarily implies that the models contain states with fractional electric charge. Such states are severely restricted by observations, and must be confined or sufficiently massive and diluted. We construct the first quasi-realistic heterotic string models in which the exotic states do not appear in the massless spectrum, and only exist, as they must, in the massive spectrum. The SO(10) GUT symmetry is broken to the Pati-Salam subgroup. Our PS heterotic string models contain adequate Higgs representations to break the GUT and electroweak symmetry, as well as colour Higgs triplets that can be used for the missing partner mechanism. By statistically sampling the space of Pati-Salam vacua we demonstrate the abundance of quasi-realistic three generation models that are completely free of massless exotics, rendering it plausible that obtaining realistic Yukawa couplings may be possible in this space of models.

  6. Interactions Between Wetlands and Tidal Inlets

    Science.gov (United States)

    2008-08-01

    Madre, TX), (3) fjord-type (e.g., Penobscot Bay , ME), and (4) tectonically created estuaries (e.g., San Francisco Bay , CA) (Pritchard 1967). This CHETN...small marsh island in San Francisco Bay , CA. Wolaver et al. (1988) measured suspended sediment flux of 827 g/m2/year into a marsh in North Inlet, SC...permanent or ephemeral inlets. Conversely, the development or construction of wetlands within an estuary reduces bay area and the tidal prism, which will

  7. Effect of piano-key shape inlet on critical submergence at a vertical pipe intake

    Science.gov (United States)

    Shemshi, R.; Kabiri-Samani, A.

    2012-11-01

    Intake vortices are the result of angular momentum conservation at the flow constriction, where angular velocity increases with a decrease in the cross sectional area. The common solution for avoiding air-entrainment and swirl is to provide sufficient submergence to the intake. If the required approach flow conditions can not be met to avoid swirl and air entrainment, other approaches for preventing vortices at water intakes are considered. There are several means of avoiding air-entrainment, where the most cost-effective option is often determined by a physical model study. Among the most economical and common measures of reducing the effect of air-entrainment and swirl strength, is the optimized shape of inlet for instance by installing a Piano-Key inlet over the pipe intake. If Piano-Key inlet is used, then, its' optimum geometry should be studied experimentally. Since there is not any realized guidance for the use of Piano-Key inlets in pipe intakes, hence, a comprehensive set of model experiments have been carried out using Piano-Key inlets with different dimensions, with respect to the vertical pipe intakes, and four different pipe diameters of (D=) 75, 100, 125 and 150 mm. Results showed that by employing a Piano-Key inlet over the vertical pipe intake, the critical submergence reduces significantly. Fianally, according to the results, the effect of Piano-Key inlet geometry on critical submergence were evaluated in the form of realized relationships which would be of practical interest for design engineers.

  8. Toward Realistic Simulation of low-Level Clouds Using a Multiscale Modeling Framework With a Third-Order Turbulence Closure in its Cloud-Resolving Model Component

    Science.gov (United States)

    Xu, Kuan-Man; Cheng, Anning

    2010-01-01

    This study presents preliminary results from a multiscale modeling framework (MMF) with an advanced third-order turbulence closure in its cloud-resolving model (CRM) component. In the original MMF, the Community Atmosphere Model (CAM3.5) is used as the host general circulation model (GCM), and the System for Atmospheric Modeling with a first-order turbulence closure is used as the CRM for representing cloud processes in each grid box of the GCM. The results of annual and seasonal means and diurnal variability are compared between the modified and original MMFs and the CAM3.5. The global distributions of low-level cloud amounts and precipitation and the amounts of low-level clouds in the subtropics and middle-level clouds in mid-latitude storm track regions in the modified MMF show substantial improvement relative to the original MMF when both are compared to observations. Some improvements can also be seen in the diurnal variability of precipitation.

  9. Numerical Simulation of NOx Formation in Coal Combustion with Inlet Natural Gas Burning

    Institute of Scientific and Technical Information of China (English)

    张宇; 周力行; 魏小林; 盛宏至

    2005-01-01

    A full two-fluid model of reacting gas-particle flows and coal combustion is used to simulate coal combustion with and without inlet natural gas added in the inlet. The simulation results for the case without natural gas burning is in fair agreement with the experimental results reported in references. The simulation results of different natural gas adding positions indicate that the natural gas burning can form lean oxygen combustion enviroment at the combustor inlet region and the NOx concentration is reduced. The same result can be obtained from chemical equilibrium analysis.

  10. Numerical study of unsteady starting characteristics of a hypersonic inlet

    Institute of Scientific and Technical Information of China (English)

    Wang Weixing; Guo Rongwei

    2013-01-01

    The impulse and self starting characteristics of a mixed-compression hypersonic inlet designed at Mach number of 6.5 are studied by applying the unsteady computational fluid dynamics (CFD) method.The full Navier-Stokes equations are solved with the assumption of viscous perfect gas model,and the shear-stress transport (SST) k-ω two-equation Reynolds averaged NavierStokes (RANS) model is used for turbulence modeling.Results indicate that during impulse starting,the flow field is divided into three zones with different aerodynamic parameters by primary shock and upstream-facing shock.The separation bubble on the shoulder of ramp undergoes a generating,growing,swallowing and disappearing process in sequence.But a separation bubble at the entrance of inlet exists until the freestream velocity is accelerated to the starting Mach number during self starting.The mass flux distribution of flow field is non-uniform because of the interaction between shock and boundary layer,so that the mass flow rate at throat is unsteady during impulse starting.The duration of impulse starting process increases almost linearly with the decrease of fleestream Mach number but rises abruptly when the freestream Mach number approaches the starting Mach number.The accelerating performance of booster almost has no influence on the self starting ability of hypersonic inlet.

  11. Dynamical Symmetries Reflected in Realistic Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Sviratcheva, K.D.; Draayer, J.P.; /Louisiana State U.; Vary, J.P.; /Iowa State U. /LLNL, Livermore /SLAC

    2007-04-06

    Realistic nucleon-nucleon (NN) interactions, derived within the framework of meson theory or more recently in terms of chiral effective field theory, yield new possibilities for achieving a unified microscopic description of atomic nuclei. Based on spectral distribution methods, a comparison of these interactions to a most general Sp(4) dynamically symmetric interaction, which previously we found to reproduce well that part of the interaction that is responsible for shaping pairing-governed isobaric analog 0{sup +} states, can determine the extent to which this significantly simpler model Hamiltonian can be used to obtain an approximate, yet very good description of low-lying nuclear structure. And furthermore, one can apply this model in situations that would otherwise be prohibitive because of the size of the model space. In addition, we introduce a Sp(4) symmetry breaking term by including the quadrupole-quadrupole interaction in the analysis and examining the capacity of this extended model interaction to imitate realistic interactions. This provides a further step towards gaining a better understanding of the underlying foundation of realistic interactions and their ability to reproduce striking features of nuclei such as strong pairing correlations or collective rotational motion.

  12. Numerical Analysis of Supersonic Film Cooling in Supersonic Flow in Hypersonic Inlet with Isolator

    Directory of Open Access Journals (Sweden)

    Silong Zhang

    2014-02-01

    Full Text Available Supersonic film cooling is an efficient method to cool the engine with extremely high heat load. In order to study supersonic film cooling in a real advanced engine, a two-dimensional model of the hypersonic inlet in a scramjet engine with supersonic film cooling in the isolator is built and validated through experimental data. The simulation results show that the cooling effect under different coolant injection angles does not show clear differences; a small injection angle can ensure both the cooling effect and good aerodynamic performances (e.g., flow coefficient of the hypersonic inlet. Under selected coolant injection angle and inlet Mach number, the cooling efficiency increases along with the injection Mach number of the coolant flow, only causing a little total pressure loss in the isolator. Along with the increase of the inlet Mach number of the hypersonic inlet, the cooling efficiency does not present a monotonic change because of the complex shock waves. However, the wall temperature shows a monotonic increase when the inlet Mach number increases. The mass flow rate of coolant flow should be increased to cool the engine more efficiently according to the mass flow rate of the main stream when the inlet Mach number increases.

  13. Should scientific realists be platonists?

    DEFF Research Database (Denmark)

    Busch, Jacob; Morrison, Joe

    2015-01-01

    Realists about are arrived at by any inferen- tial route which eschews causes (§3), and nor is there any direct pressure for Scientific Real- ists to change their inferential methods (§4). We suggest that in order to maintain inferential parity with Scientific Realism, proponents of EIA need to give......Enhanced Indispensability Arguments (EIA) claim that Scientific Realists are committed to the existence of mathematical entities due to their reliance on Inference to the Best Explana- tion (IBE). Our central question concerns this purported parity of reasoning: do people who defend the EIA make...... an appropriate use of the resources of Scientific Realism (in particular, IBE) to achieve platonism? (§2) We argue that just because a variety of different inferential strategies can be employed by Scientific Realists does not mean that ontological conclusions concerning which things we should be Scientific...

  14. Realistic level density calculation for heavy nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Cerf, N. [Institut de Physique Nucleaire, Orsay (France); Pichon, B. [Observatoire de Paris, Meudon (France); Rayet, M.; Arnould, M. [Institut d`Astronomie et d`Astrophysique, Bruxelles (Belgium)

    1994-12-31

    A microscopic calculation of the level density is performed, based on a combinatorial evaluation using a realistic single-particle level scheme. This calculation relies on a fast Monte Carlo algorithm, allowing to consider heavy nuclei (i.e., large shell model spaces) which could not be treated previously in combinatorial approaches. An exhaustive comparison of the predicted neutron s-wave resonance spacings with experimental data for a wide range of nuclei is presented.

  15. Mean water level setup/setdown in the inlet-lagoon system induced by tidal action-a case study of Xincun Inlet, Hainan Island in China

    Institute of Scientific and Technical Information of China (English)

    GONG Wenping; SHEN Jian; WANG Daoru

    2008-01-01

    With the tides propagating from the open sea to the lagoon, the mean water level (MWL) in the inlet and lagoon becomes different from that at the open sea, and a setup/setdown is generated. The change of MWL (setup/setdown) in the system imposes a great impact on regulating the development of tidal marshes, on determining the long-term water level for harbor maintenance, on the planning for the water front development with the flood control for the possible inundation, and on the interpretation of the historical sea level change when using tidal marsh peat deposits in the lagoon as the indicator for open sea' s sea level. In this ease study on the mechanisms which control the setup/setdown in Xincun Inlet, Hainan in China, the 2-D barotropic mode of Eulerian - Lagrangian CIRCulation (ELCIRC) model was utilized. After model calibration and verification, a series of numerical experiments were conducted to examine the effects of bottom friction and advection terms, wetting and drying of intertidal areas, bathymetry and boundary conditions on the setup/setdown in the system. The modeling results show that setup occurs over the inlet and lagoon areas with an order of one tenth of the tide range at the entrance. The larger the bottom friction is, a larger setup is generated.Without the advection term, the setup is reduced due to a decrease of water level gradient to compensate for the disappearance of the advection term. Even without overtides, a setup can still be developed in the system. Sea level rise and dredging in the inlet and tidal channel can cause a decrease of setup in the system, whereas shoaling of the system can increase the setup. The uniqueness of the Xincun Inlet with respect to MWL change is that there is no evident setdown in the inlet, which can be attributed to the complex geometry and bathymetry associated with the inlet system.

  16. Development of an Inlet Pressure Sensor for Control in a Left Ventricular Assist Device

    OpenAIRE

    2010-01-01

    A Tesla type continuous flow left ventricular assist device (VAD) has been designed by Penn State and Advanced Bionics, Inc. (ABI). When a continuous flow device is employed, care must be taken to limit low pressures in the ventricle that can produce an obstruction to the inlet cannula or trigger arrhythmias. Design of an inexpensive, semi-conductor strain gage inlet pressure sensor to detect suction has been completed. The research and design analysis included finite element modeling of the ...

  17. INCREASED CAPACITY OF THE UNDERSTANDING OF THE CONCEPT AND THE ABILITY TO SOLVE PROBLEMS THROUGH THE IMPLEMENTATION OF THE MODEL OF TEACHING MATHEMATICS REALISTIC BASED ON COGNITIVE CONFLICT STUDENTS

    Directory of Open Access Journals (Sweden)

    Dewi Herawaty

    2016-10-01

    Full Text Available This research aims at: 1 the influence of the implementation of the model of teaching mathematics realistic based on cognitive conflict students to the ability to understanding the concept and troubleshooting capabilities; 2 determine the larger capacity of the understanding of the concept through the implementation of the model of teaching mathematics realistic based on cognitive conflict junior secondary school students the City of Bengkulu. 3 determine the great improvement of the ability to solve problems through the implementation of the model of teaching mathematics realistic based on cognitive conflict SMP students Bengkulu City.To achieve the goal of this research is to apply Research Design pseudo experiments with research design Pretest-Postest Nonequivalent Control Group Design, with the test instrument the ability to understanding the concept and test the troubleshooting capabilities. The data has been analyzed using the test gains. The results of this research is 1 the ability of understanding the concept and troubleshooting class experiment the given learning with PMR is better than with the ability to understanding the concept and troubleshooting control classes assigned to conventional mathematics lesson; 2 increase the ability of the understanding of the concept through the implementation of the model of teaching mathematics based on cognitive conflict SMP students Bengkulu City is significant with the index gain of 0,755 (high-level; 3 increase the ability to solve problems through the implementation of the model of teaching mathematics based on cognitive conflict SMP students Bengkulu City is significant with the index gain of 0,500 level (is.

  18. Time management: a realistic approach.

    Science.gov (United States)

    Jackson, Valerie P

    2009-06-01

    Realistic time management and organization plans can improve productivity and the quality of life. However, these skills can be difficult to develop and maintain. The key elements of time management are goals, organization, delegation, and relaxation. The author addresses each of these components and provides suggestions for successful time management.

  19. Assessment and realistic mathematics education

    NARCIS (Netherlands)

    Heuvel-Panhuizen, M.H.A.M. van den

    1996-01-01

    This book describes the consequences of Realistic Mathematics Education (RME) for assessing students’ understanding of mathematics in primary school. RME is the Dutch answer to the worldwide need to reform mathematics education. Changed ideas about mathematics as a school subject, its goals, ideas a

  20. Probabilistic Bisimulation for Realistic Schedulers

    DEFF Research Database (Denmark)

    Eisentraut, Christian; Godskesen, Jens Christian; Hermanns, Holger

    2015-01-01

    . This holds in the classical context of arbitrary schedulers, but it has been argued that this class of schedulers is unrealistically powerful. This paper studies a strictly coarser notion of bisimilarity, which still enjoys these properties in the context of realistic subclasses of schedulers: Trace...

  1. Assessment and realistic mathematics education

    NARCIS (Netherlands)

    Heuvel-Panhuizen, M.H.A.M. van den

    1996-01-01

    This book describes the consequences of Realistic Mathematics Education (RME) for assessing students’ understanding of mathematics in primary school. RME is the Dutch answer to the worldwide need to reform mathematics education. Changed ideas about mathematics as a school subject, its goals,

  2. Presupernova neutrinos: realistic emissivities from stellar evolution

    CERN Document Server

    Patton, Kelly M

    2015-01-01

    We present a new calculation of neutrino emissivities and energy spectra from a presupernova, a massive star going through the advanced stages of nuclear burning in the months before becoming a supernova. The contributions from beta decay and electron capture, pair annihilation, plasmon decay, and the photoneutrino process are modeled in detail, using updated tabulated nuclear rates. We also use realistic conditions of temperature, density, electron fraction and nuclear isotopic composition of the star from the state of the art stellar evolution code MESA. It is found that beta processes contribute substantially to the neutrino flux above realistic detection thresholds of few MeV, at selected positions and times in the evolution of the star.

  3. Thermography of the New River Inlet plume and nearshore currents

    Science.gov (United States)

    Chickadel, C.; Jessup, A.

    2012-12-01

    As part of the DARLA and RIVET experiments, thermal imaging systems mounted on a tower and in an airplane captured water flow in the New River Inlet, NC, USA. Kilometer-scale, airborne thermal imagery of the inlet details the ebb flow of the estuarine plume water mixing with ocean water. Multiple fronts, corresponding to the preferred channels through the ebb tidal delta, are imaged in the aerial data. A series of internal fronts suggest discreet sources of the tidal plume that vary with time. Focused thermal measurements made from a tower on the south side of the inlet viewed an area within a radius of a few hundred meters. Sub-meter resolution video from the tower revealed fine-scale flow features and the interaction of tidal exchange and wave-forced surfzone currents. Using the tower and airborne thermal image data we plan to provide geophysical information to compare with numerical models and in situ measurements made by other investigators. From the overflights, we will map the spatial and temporal extent of the estuarine plume to correlate with tidal phase and local wind conditions. From the tower data, we will investigate the structure of the nearshore flow using a thermal particle image velocimetry (PIV) technique, which is based on tracking motion of the surface temperature patterns. Long term variability of the mean and turbulent two-dimensional PIV currents will be correlated to local wave, tidal, and wind forcing parameters.

  4. Modeling of the inlet and exhaust manifolds by using the wave action and her influence on the accuracy of the results obtained from the internal combustion engines simulator program; Modelagem dos coletores de admissao e descarga pelo metodo da acao das ondas e sua influencia sobre a precisao dos resultados do programa simulador de motores de combustao interna

    Energy Technology Data Exchange (ETDEWEB)

    Vianna, Joao Nildo de S.; Oliveira, Guilherme L. de; Oliveira, Lucio H.H. de [Brasilia Univ., DF (Brazil). Dept. de Engenharia Mecanica

    1996-07-01

    This work presents a comparative study of the performance of a simulation computer program where the inlet and exhaust manifolds are modeled by the control volume method and the by the wave action method. Results obtained by both methods are compared with experimental data. To validate the method of wave action an exhaust manifold wa specifically built. The results show that the wave action method improves considerably the performance of the simulation software, although it increases the processing time. (author)

  5. True-to-Life? Realistic Fiction.

    Science.gov (United States)

    Jordan, Anne Devereaux

    1995-01-01

    Suggests that modern realistic fiction for young readers is intensely moralistic and directive at the spoken and unspoken behest of the adults who write, select, and buy that literature. Discusses moral tales, early realistic fiction, modern realistic fiction, and choosing realistic fiction. (RS)

  6. True-to-Life? Realistic Fiction.

    Science.gov (United States)

    Jordan, Anne Devereaux

    1995-01-01

    Suggests that modern realistic fiction for young readers is intensely moralistic and directive at the spoken and unspoken behest of the adults who write, select, and buy that literature. Discusses moral tales, early realistic fiction, modern realistic fiction, and choosing realistic fiction. (RS)

  7. The influence of boundary layers on supersonic inlet flow unstart induced by mass injection

    Science.gov (United States)

    Do, Hyungrok; Im, Seong-Kyun; Mungal, M. Godfrey; Cappelli, Mark A.

    2011-09-01

    A transverse jet is injected into a supersonic model inlet flow to induce unstart. Planar laser Rayleigh scattering from condensed CO2 particles is used to visualize flow dynamics during the unstart process, while in some cases, wall pressure traces are simultaneously recorded. Studies conducted over a range of inlet configurations reveal that the presence of turbulent wall boundary layers strongly affect the unstart dynamics. It is found that relatively thick turbulent boundary layers in asymmetric wall boundary layer conditions prompt the formation of unstart shocks; in symmetric boundary conditions lead to the propagation of pseudo-shocks; and in both cases facilitate fast inlet unstart, when compared with thin, laminar boundary layers. Incident shockwaves and associated reflections are found to affect the speed of pressure disturbances. These disturbances, which induce boundary layer separation, are found to precede the formation of unstart shocks. The results confirm the importance of and need to better understand shock-boundary layer interactions in inlet unstart dynamics.

  8. CFD simulation of inlet design effect on deoiling hydrocyclone separation efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Noroozi, S.; Hashemabadi, S.H. [Computational Fluid Dynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

    2009-12-15

    An Eulerian-Eulerian three-dimensional CFD model was developed to study the effect of different inlet designs on deoiling hydrocyclone separation efficiency. Reynolds averaged Navier Stokes and continuity equations were applied to solve steady turbulent flow through the cyclone with the Reynolds stress model. In addition, the modified drag correlation for liquid-liquid emulsion with respect to the Reynolds number range and viscosity ratio of two phases was used and the simulation results were compared with those predicted by the Schiller-Naumann correlation. Pressure profile, tangential and axial velocities and separation efficiency of the deoiling hydrocyclone were calculated for four different inlet designs and compared with the standard design. The simulation results for the standard design demonstrate an acceptable agreement with reported experimental data. The results show that all new four inlet designs offer higher efficiencies compared to the standard design. The difference between the efficiency of the LLHC, of the new inlets and the standard design can be improved by increasing the inlet velocity. Furthermore, the simulations show that the separation efficiency can be improved by about 10 % when using a helical form of inlet. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  9. Realist Criminology and its Discontents

    Directory of Open Access Journals (Sweden)

    Simon Winlow

    2016-09-01

    Full Text Available Critical criminology must move beyond twentieth-century empiricist and idealist paradigms because the concepts and research programmes influenced by these paradigms are falling into obsolescence. Roger Matthews’ recent work firmly advocates this position and helps to set the ball rolling. Here we argue that Matthews’ attempt to use critical realist thought to move Left Realism towards an advanced position can help to put criminology on a sound new footing. However, before this becomes possible numerous philosophical and theoretical issues must be ironed out. Most importantly, critical criminology must avoid political pragmatism and adopt a more critical stance towards consumer culture’s spectacle. A searching analysis of these issues suggests that, ultimately, criminology is weighed down with obsolete thinking to such an extent that to remain intellectually relevant it must move beyond both Left Realism and Critical Realism to construct a new ultra-realist position.

  10. Cold water inlet in solar tanks - valuation

    DEFF Research Database (Denmark)

    Andersen, Elsa

    1999-01-01

    The aim of the project is to make a proposal for how to value a storage tank with a poor design of the cold water inlet. Based on measurements and calculations a number of curves, which are valid for this valuation, are worked out. Based on a simple test with a uniform heated storage tank the ratio...

  11. Miniature piezo electric vacuum inlet valve

    Science.gov (United States)

    Keville, Robert F.; Dietrich, Daniel D.

    1998-03-24

    A miniature piezo electric vacuum inlet valve having a fast pulse rate and is battery operated with variable flow capability. The low power (piezo electric valves which require preloading of the crystal drive mechanism and 120 Vac, thus the valve of the present invention is smaller by a factor of three.

  12. Assessment and realistic mathematics education

    OpenAIRE

    Heuvel-Panhuizen, M.H.A.M. van den

    1996-01-01

    This book describes the consequences of Realistic Mathematics Education (RME) for assessing students’ understanding of mathematics in primary school. RME is the Dutch answer to the worldwide need to reform mathematics education. Changed ideas about mathematics as a school subject, its goals, ideas about teaching and learning mathematics, require new forms of assessment. Within RME this means a preference for observation and individual interviews. However, written tests have not been abandoned...

  13. Effect of inlet and outlet flow conditions on natural gas parameters in supersonic separation process.

    Directory of Open Access Journals (Sweden)

    Yan Yang

    Full Text Available A supersonic separator has been introduced to remove water vapour from natural gas. The mechanisms of the upstream and downstream influences are not well understood for various flow conditions from the wellhead and the back pipelines. We used a computational model to investigate the effect of the inlet and outlet flow conditions on the supersonic separation process. We found that the shock wave was sensitive to the inlet or back pressure compared to the inlet temperature. The shock position shifted forward with a higher inlet or back pressure. It indicated that an increasing inlet pressure declined the pressure recovery capacity. Furthermore, the shock wave moved out of the diffuser when the ratio of the back pressure to the inlet one was greater than 0.75, in which the state of the low pressure and temperature was destroyed, resulting in the re-evaporation of the condensed liquids. Natural gas would be the subsonic flows in the whole supersonic separator, if the mass flow rate was less than the design value, and it could not reach the low pressure and temperature for the condensation and separation of the water vapor. These results suggested a guidance mechanism for natural gas supersonic separation in various flow conditions.

  14. Effects of inlet momentum and orientation on the hydraulic performance of water storage tanks

    Science.gov (United States)

    Xavier, Manoel Lucas Machado; Janzen, Johannes Gérson

    2017-09-01

    The influence of inlet momentum and inlet orientation on hydraulic performance of cylindrical water process tanks were investigated using a factorial design strategy. The hydraulic performance of the tanks was assessed with a computational fluid dynamics (CFD) model, which calculated the flow fields and the residence time distribution (RTD). RTDs were used to quantify the tanks hydraulic performance using hydraulic indexes that represent short-circuiting, mixing, and moment. These indexes were later associated with the effluent fraction of disinfectant (inlet and outlet disinfectant ratio). For small depth-to-diameter ratios, the inlet orientation and the inlet momentum were the most important factors regarding the hydraulic indexes and the effluent fraction of disinfectant, respectively. A poor correlation was obtained between the hydraulic indexes and the effluent fraction of disinfectant, indicating that they are not good predictors for water quality. For large depth-to-diameter ratios, the inlet orientation had the most significant effect on both the hydraulic indexes and effluent fraction of disinfectant. The short-circuiting and mixing indexes presented a good correlation with water quality for this case.

  15. Numerical investigation of the effect of number and shape of inlet of cyclone and particle size on particle separation

    Science.gov (United States)

    Khazaee, Iman

    2016-12-01

    Cyclones are one of the most common devices for removing particles from the gas stream and act as a filter. The mode of action of separating these particles, from mass gas flow, in this case, is that the inertia force exerted on the solid particles in the cyclone, several times greater than the force of inertia into the gas phase and so the particles are guided from the sides of the cyclone body to the bottom body but less power will be affected by the gas phase and from upper parts, solid particles, goes to the bottom chamber. Most of the attention has been focused on finding new methods to improve performance parameters. Recently, some studies were conducted to improve equipment performance by evaluating geometric effects on projects. In this work, the effect of cyclone geometry was studied through the creation of a symmetrical double and quad inlet and also studied cutting inlet geometry and their influence on separation efficiency. To assess the accuracy of modeling, selected model compared with the model Kim and Lee and the results were close to acceptable. The collection efficiency of the double inlet cyclone was found to be 20-25% greater than that of the single inlet cyclone and the collection efficiency of the quad inlet cyclone was found to be 40-45% greater than with the same inlet size. Also the collection efficiency of the rectangle inlet was found to be 4-6% greater than ellipse inlet and the collection efficiency of the ellipse inlet was found to be 30-35% greater than circle inlet.

  16. Inlet flow distortion in turbomachinery

    Science.gov (United States)

    Seidel, B. S.; Matwey, M. D.; Adamczyk, J. J.

    1980-01-01

    A single stage axial compressor with distorted inflow is studied. The inflow distortion occurs far upstream and may be a distortion in stagnation temperature, stagnation pressure or both. The blade rows are modeled as semi-actuator disks. Losses, quasi-steady deviation angles, and reference incidence correlations are included in the analysis. Both subsonic and transonic relative Mach numbers are considered. A parameter study is made to determine the influence of such variables as Mach number and swirl angle on the attenuation of the distortion.

  17. Flow Control in a Compact Inlet

    Science.gov (United States)

    Vaccaro, John C.

    2011-12-01

    An experimental investigation of flow control, via various control jets actuators, was undertaken to eliminate separation and secondary flows in a compact inlet. The compact inlet studied was highly aggressive with a length-to-diameter ratio of 1.5. A brand new facility was designed and built to enable various actuation methodologies as well as multiple measurement techniques. Techniques included static surface pressure, total pressure, and stereoscopic particle image velocimetry. Experimental data were supplemented with numerical simulations courtesy of Prof. Kenneth Jansen, Dr. Onkar Sahni, and Yi Chen. The baseline flow field was found to be dominated by two massive separations and secondary flow structures. These secondary structures were present at the aerodynamic interface plane in the form of two counter-rotating vortices inducing upwash along centerline. A dominant shedding frequency of 350 Hz was measured both at the aerodynamic interface plane and along the lower surface of the inlet. Flow control experiments started utilizing a pair of control jets placed in streamwise locations where flow was found to separate. Tests were performed for a range of inlet Mach numbers from 0.2 to 0.44. Steady and unsteady static pressure measurements along the upper and lower walls of the duct were performed for various combinations of actuation. The parameters that were tested include the control jets momentum coefficient, their blowing ratio, the actuation frequency, as well as different combinations of jets. It was shown that using mass flux ratio as a criterion to define flow control is not sufficient, and one needs to provide both the momentum coefficient and the blowing ratio to quantify the flow control performance. A detailed study was undertaken on controlling the upstream separation point for an inlet Mach number of 0.44. Similar to the baseline flow field, the flow field associated with the activation of a two-dimensional control jet actuator was dominated by

  18. New inlet nozzle assembly: C Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Calkin, J.F.

    1960-10-19

    The use of self-supported fuel elements in ribless Zircaloy-2 tubes at C-Reactor requires some inlet nozzle modification to allow charging of the larger overall diameter fuel pieces. A new nozzle assembly has been developed (by Equipment Development Operation -- IPD) which will allow use of the new fuel pieces and at the same time increase the reliability of the header-to-tube piping and reduce pumping power losses. Flow test data were requested for the new assembly and the results of these tests are presented herein. This report also presents a comparison of the header to tube energy losses for the various reactor inlet nozzle assemblies which are currently used on the Hanford production reactors.

  19. Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions

    Science.gov (United States)

    Wißdorf, Walter; Müller, David; Brachthäuser, Yessica; Langner, Markus; Derpmann, Valerie; Klopotowski, Sebastian; Polaczek, Christine; Kersten, Hendrik; Brockmann, Klaus; Benter, Thorsten

    2016-09-01

    In this work, the characteristics of gas flow in inlet capillaries are examined. Such inlet capillaries are widely used as a first flow restriction stage in commercial atmospheric pressure ionization mass spectrometers. Contrary to the common assumption, we consider the gas flow in typical glass inlet capillaries with 0.5 to 0.6 mm inner diameters and lengths about 20 cm as transitional or turbulent. The measured volume flow of the choked turbulent gas stream in such capillaries is 0.8 L·min-1 to 1.6 L·min-1 under typical operation conditions, which is in good agreement to theoretically calculated values. Likewise, the change of the volume flow in dependence of the pressure difference along the capillary agrees well with a theoretical model for turbulent conditions as well as with exemplary measurements of the static pressure inside the capillary channel. However, the results for the volume flow of heated glass and metal inlet capillaries are neither in agreement with turbulent nor with laminar models. The velocity profile of the neutral gas in a quartz capillary with an inner diameter similar to commercial inlet capillaries was experimentally determined with spatially resolved ion transfer time measurements. The determined gas velocity profiles do not contradict the turbulent character of the flow. Finally, inducing disturbances of the gas flow by placing obstacles in the capillary channel is found to not change the flow characteristics significantly. In combination the findings suggest that laminar conditions inside inlet capillaries are not a valid primary explanation for the observed high ion transparency of inlet capillaries under common operation conditions.

  20. Tidal hydrodynamics in a two-inlet coastal lagoon in the Gulf of California

    Science.gov (United States)

    Serrano, David; Ramírez-Félix, Evlin; Valle-Levinson, Arnoldo

    2013-07-01

    The aim of this study is to understand the effects of friction and advection in the hydrodynamics of a two-inlet coastal lagoon, Santa María La Reforma, in Northwest Mexico. A vertically integrated numerical model is used to describe sea level variations and tidal currents, and to study the dynamics inside the system. Observed sea level and current measurements were used to calibrate the model. Results show a ˜90 min phase lag of the tidal signal in the center of the system with respect to both inlets. Tidal currents greater than 1.0 m s-1 were recorded and modeled at both inlets. The sea level in the lagoon shows one-quarter of period of M2 out of phase (˜3 h) with respect to the velocity. Bottom friction generated the greatest M4 harmonic and largest tidal asymmetries at the narrowest section of the lagoon, ˜35 km away from the inlets. The tidal momentum balance along the main axis of the lagoon was dominated by pressure gradient and friction, describing a quasi-standing tidal wave in currents and in amplitude. This behavior resulted from waves traveling in opposite directions from the two tidal inlets, causing constructive interference in elevation but destructive interference inflow.